diff --git a/client/src/components/room/AnswerJudgeResult.fixture.ts b/client/src/components/room/AnswerJudgeResult.fixture.ts
new file mode 100644
index 0000000..a2ad442
--- /dev/null
+++ b/client/src/components/room/AnswerJudgeResult.fixture.ts
@@ -0,0 +1,35 @@
+import type { components } from '@/generated/api'
+import { mockContract } from '@/mocks/data'
+
+type AnswerResponse = components['schemas']['AnswerResponse']
+
+function getAnswerFixture(
+  example: 'incorrect_answer' | 'correct_answer_unlocks_problem',
+): AnswerResponse {
+  return mockContract.getResponseExample('submitAnswer', 200, example) as AnswerResponse
+}
+
+function judgeStateFromAnswer(response: AnswerResponse) {
+  return response.correct ? ('correct' as const) : ('incorrect' as const)
+}
+
+const incorrectAnswer = getAnswerFixture('incorrect_answer')
+const correctAnswer = getAnswerFixture('correct_answer_unlocks_problem')
+
+export const answerJudgeResultFixtures = {
+  idle: {
+    state: 'idle',
+  },
+  pending: {
+    state: 'pending',
+  },
+  correct: {
+    state: judgeStateFromAnswer(correctAnswer),
+  },
+  incorrect: {
+    state: judgeStateFromAnswer(incorrectAnswer),
+  },
+  error: {
+    state: 'error',
+  },
+} as const
diff --git a/client/src/components/room/AnswerJudgeResult.story.vue b/client/src/components/room/AnswerJudgeResult.story.vue
new file mode 100644
index 0000000..033410c
--- /dev/null
+++ b/client/src/components/room/AnswerJudgeResult.story.vue
@@ -0,0 +1,38 @@
+<script setup lang="ts">
+import AnswerJudgeResult from './AnswerJudgeResult.vue'
+import { answerJudgeResultFixtures } from './AnswerJudgeResult.fixture'
+</script>
+
+<template>
+  <Story title="Room/AnswerJudgeResult">
+    <Variant title="判定待ち">
+      <div class="w-80 bg-[#eef4ff] p-4">
+        <AnswerJudgeResult v-bind="answerJudgeResultFixtures.idle" />
+      </div>
+    </Variant>
+
+    <Variant title="判定中">
+      <div class="w-80 bg-[#eef4ff] p-4">
+        <AnswerJudgeResult v-bind="answerJudgeResultFixtures.pending" />
+      </div>
+    </Variant>
+
+    <Variant title="正解">
+      <div class="w-80 bg-[#eef4ff] p-4">
+        <AnswerJudgeResult v-bind="answerJudgeResultFixtures.correct" />
+      </div>
+    </Variant>
+
+    <Variant title="不正解">
+      <div class="w-80 bg-[#eef4ff] p-4">
+        <AnswerJudgeResult v-bind="answerJudgeResultFixtures.incorrect" />
+      </div>
+    </Variant>
+
+    <Variant title="エラー">
+      <div class="w-80 bg-[#eef4ff] p-4">
+        <AnswerJudgeResult v-bind="answerJudgeResultFixtures.error" />
+      </div>
+    </Variant>
+  </Story>
+</template>
diff --git a/client/src/components/room/AnswerJudgeResult.vue b/client/src/components/room/AnswerJudgeResult.vue
new file mode 100644
index 0000000..ce20f4f
--- /dev/null
+++ b/client/src/components/room/AnswerJudgeResult.vue
@@ -0,0 +1,85 @@
+<script setup lang="ts">
+import { computed, useId } from 'vue'
+
+type JudgeState = 'idle' | 'pending' | 'correct' | 'incorrect' | 'error'
+
+interface AnswerJudgeResultProps {
+  state: JudgeState
+}
+
+const props = defineProps<AnswerJudgeResultProps>()
+const titleId = useId()
+
+const presentationByState = {
+  idle: {
+    label: '判定待ち',
+    description: '回答すると結果が表示されます',
+    symbol: '—',
+    badgeClasses: 'bg-[#eef3fa] text-[#52627a]',
+  },
+  pending: {
+    label: '判定中',
+    description: '回答を判定しています',
+    symbol: '…',
+    badgeClasses: 'bg-[#e7f0ff] text-[#2463d4]',
+  },
+  correct: {
+    label: '正解',
+    description: '回答は正解です',
+    symbol: '○',
+    badgeClasses: 'bg-[#ddf8e8] text-[#159447]',
+  },
+  incorrect: {
+    label: '不正解',
+    description: '回答は不正解です',
+    symbol: '×',
+    badgeClasses: 'bg-[#ffebec] text-[#d63844]',
+  },
+  error: {
+    label: '判定エラー',
+    description: '判定結果を取得できませんでした',
+    symbol: '!',
+    badgeClasses: 'bg-[#fff1da] text-[#a85c00]',
+  },
+} satisfies Record<
+  JudgeState,
+  {
+    label: string
+    description: string
+    symbol: string
+    badgeClasses: string
+  }
+>
+
+const presentation = computed(() => presentationByState[props.state])
+</script>
+
+<template>
+  <section
+    class="flex min-h-72 w-full flex-col items-center rounded-xl border border-[#cbd8e9] bg-white px-6 py-5 text-[#152238] shadow-sm"
+    :aria-labelledby="titleId"
+    aria-live="polite"
+    aria-atomic="true"
+    :aria-busy="state === 'pending' ? 'true' : undefined"
+    :data-state="state"
+  >
+    <h2 :id="titleId" class="text-sm font-bold">判定結果</h2>
+
+    <div
+      class="mt-4 flex h-24 w-24 items-center justify-center rounded-full"
+      :class="presentation.badgeClasses"
+      data-testid="result-badge"
+    >
+      <span class="text-5xl font-bold leading-none" aria-hidden="true" data-testid="result-symbol">
+        {{ presentation.symbol }}
+      </span>
+    </div>
+
+    <p class="mt-3 text-base font-bold" data-testid="result-label">
+      {{ presentation.label }}
+    </p>
+    <p class="mt-1 text-center text-xs text-[#718099]">
+      {{ presentation.description }}
+    </p>
+  </section>
+</template>
diff --git a/client/src/components/room/AnswerPanel.fixture.ts b/client/src/components/room/AnswerPanel.fixture.ts
new file mode 100644
index 0000000..fb63d9d
--- /dev/null
+++ b/client/src/components/room/AnswerPanel.fixture.ts
@@ -0,0 +1,20 @@
+import type { components } from '@/generated/api'
+import { mockContract } from '@/mocks/data'
+
+type ProblemResponse = components['schemas']['ProblemResponse']
+type AnswerRequest = components['schemas']['AnswerRequest']
+
+const problem = mockContract.getResponseExample(
+  'getProblem',
+  200,
+  'available_problem',
+) as ProblemResponse
+const submittedAnswer = mockContract.getRequestExample(
+  'submitAnswer',
+  'submitted_answer',
+) as AnswerRequest
+
+export const answerPanelFixture = {
+  maxLength: problem.input_schema.answer.max_length,
+  submittedAnswer: submittedAnswer.answer,
+} as const
diff --git a/client/src/components/room/AnswerPanel.story.vue b/client/src/components/room/AnswerPanel.story.vue
new file mode 100644
index 0000000..f1b5676
--- /dev/null
+++ b/client/src/components/room/AnswerPanel.story.vue
@@ -0,0 +1,25 @@
+<script setup lang="ts">
+import AnswerPanel from './AnswerPanel.vue'
+import { answerPanelFixture } from './AnswerPanel.fixture'
+</script>
+
+<template>
+  <Story title="Room/AnswerPanel">
+    <Variant title="入力可能">
+      <AnswerPanel
+        :max-length="answerPanelFixture.maxLength"
+        :pending="false"
+        :disabled="false"
+        @submit="console.log('Submit answer:', $event)"
+      />
+    </Variant>
+
+    <Variant title="送信中">
+      <AnswerPanel :max-length="answerPanelFixture.maxLength" :pending="true" :disabled="false" />
+    </Variant>
+
+    <Variant title="入力不可">
+      <AnswerPanel :max-length="answerPanelFixture.maxLength" :pending="false" :disabled="true" />
+    </Variant>
+  </Story>
+</template>
diff --git a/client/src/components/room/AnswerPanel.vue b/client/src/components/room/AnswerPanel.vue
new file mode 100644
index 0000000..059d925
--- /dev/null
+++ b/client/src/components/room/AnswerPanel.vue
@@ -0,0 +1,89 @@
+<script setup lang="ts">
+import { computed, ref, useId } from 'vue'
+
+const props = defineProps<{
+  maxLength: number
+  pending: boolean
+  disabled: boolean
+}>()
+
+const emit = defineEmits<{
+  submit: [answer: string]
+}>()
+
+const answer = ref('')
+const answerInputId = useId()
+const helpId = `${answerInputId}-help`
+const countId = `${answerInputId}-count`
+
+const interactionDisabled = computed(() => props.pending || props.disabled)
+const answerTooLong = computed(() => answer.value.length > props.maxLength)
+const submitDisabled = computed(() => interactionDisabled.value || answerTooLong.value)
+
+function submitAnswer() {
+  if (submitDisabled.value) return
+  emit('submit', answer.value)
+}
+
+function handleAnswerKeydown(event: KeyboardEvent) {
+  if (event.key !== 'Enter' || event.shiftKey || event.isComposing) return
+
+  event.preventDefault()
+  if (event.repeat) return
+
+  submitAnswer()
+}
+</script>
+
+<template>
+  <section
+    id="answer-panel"
+    class="rounded-xl border border-[#c8d5e8] bg-[#eef4ff] p-4 text-[#121a2a] sm:p-5"
+    aria-labelledby="answer-panel-title"
+    :aria-busy="pending"
+  >
+    <header class="mb-4">
+      <h2 id="answer-panel-title" class="text-base font-extrabold">回答パネル</h2>
+    </header>
+
+    <form
+      class="rounded-xl border border-[#c8d5e8] bg-white p-4 sm:p-5"
+      @submit.prevent="submitAnswer"
+    >
+      <label :for="answerInputId" class="mb-3 block text-sm font-bold">回答</label>
+      <textarea
+        :id="answerInputId"
+        v-model="answer"
+        name="answer"
+        rows="6"
+        :maxlength="maxLength"
+        :disabled="interactionDisabled"
+        :aria-describedby="`${helpId} ${countId}`"
+        class="min-h-36 w-full resize-y rounded-lg border border-[#7aa7ff] bg-[#fbfcff] px-4 py-3 text-sm text-[#121a2a] outline-none transition-shadow placeholder:text-[#8da0bd] focus:border-[#2e6bea] focus:ring-2 focus:ring-[#2e6bea]/20 disabled:cursor-not-allowed disabled:border-[#d5dce7] disabled:bg-[#f1f4f8] disabled:text-[#78869a]"
+        placeholder="答えを入力してください"
+        @keydown="handleAnswerKeydown"
+      />
+
+      <div class="mt-2 flex flex-wrap items-start justify-between gap-2 text-xs text-[#65758d]">
+        <p :id="helpId">最大{{ maxLength }}文字。Enterで送信、Shift+Enterで改行します。</p>
+        <p :id="countId" :class="answerTooLong ? 'font-bold text-red-700' : ''">
+          <span class="sr-only">入力文字数 </span>
+          {{ answer.length }}/{{ maxLength }}
+        </p>
+      </div>
+
+      <div class="mt-4 flex items-center justify-between gap-4">
+        <p class="text-xs font-bold text-[#2764d8]" aria-live="polite">
+          {{ pending ? '送信中…' : disabled ? '入力できません' : '入力待ち' }}
+        </p>
+        <button
+          type="submit"
+          :disabled="submitDisabled"
+          class="inline-flex min-h-10 min-w-20 items-center justify-center rounded-lg bg-[#2864e8] px-5 text-sm font-bold text-white transition-colors hover:bg-[#1f56cc] focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-[#3997ea] disabled:cursor-not-allowed disabled:bg-[#a7b8d8]"
+        >
+          {{ pending ? '送信中…' : '送信' }}
+        </button>
+      </div>
+    </form>
+  </section>
+</template>
diff --git a/client/src/components/room/__tests__/AnswerJudgeResult.spec.ts b/client/src/components/room/__tests__/AnswerJudgeResult.spec.ts
new file mode 100644
index 0000000..6d553ce
--- /dev/null
+++ b/client/src/components/room/__tests__/AnswerJudgeResult.spec.ts
@@ -0,0 +1,68 @@
+import { mount } from '@vue/test-utils'
+import { describe, expect, it } from 'vitest'
+
+import AnswerJudgeResult from '../AnswerJudgeResult.vue'
+import { answerJudgeResultFixtures } from '../AnswerJudgeResult.fixture'
+
+describe('AnswerJudgeResult', () => {
+  it.each([
+    ['idle', '判定待ち', '—', 'bg-[#eef3fa]'],
+    ['pending', '判定中', '…', 'bg-[#e7f0ff]'],
+    ['correct', '正解', '○', 'bg-[#ddf8e8]'],
+    ['incorrect', '不正解', '×', 'bg-[#ffebec]'],
+    ['error', '判定エラー', '!', 'bg-[#fff1da]'],
+  ] as const)('%sの文言、記号、配色を表示する', (state, label, symbol, colorClass) => {
+    const wrapper = mount(AnswerJudgeResult, {
+      props: { state },
+    })
+
+    expect(wrapper.attributes('data-state')).toBe(state)
+    expect(wrapper.get('[data-testid="result-label"]').text()).toBe(label)
+    expect(wrapper.get('[data-testid="result-symbol"]').text()).toBe(symbol)
+    expect(wrapper.get('[data-testid="result-badge"]').classes()).toContain(colorClass)
+    expect(wrapper.attributes('aria-live')).toBe('polite')
+    expect(wrapper.emitted()).toEqual({})
+  })
+
+  it('pendingの間だけbusyであることを通知する', async () => {
+    const wrapper = mount(AnswerJudgeResult, {
+      props: { state: 'idle' },
+    })
+
+    expect(wrapper.attributes('aria-busy')).toBeUndefined()
+
+    await wrapper.setProps({ state: 'pending' })
+
+    expect(wrapper.attributes('aria-busy')).toBe('true')
+
+    await wrapper.setProps({ state: 'correct' })
+
+    expect(wrapper.attributes('aria-busy')).toBeUndefined()
+  })
+
+  it('errorとincorrectを文言で区別して通知する', () => {
+    const error = mount(AnswerJudgeResult, {
+      props: { state: 'error' },
+    })
+    const incorrect = mount(AnswerJudgeResult, {
+      props: { state: 'incorrect' },
+    })
+
+    expect(error.attributes('aria-live')).toBe('polite')
+    expect(error.text()).toContain('判定結果を取得できませんでした')
+    expect(incorrect.attributes('aria-live')).toBe('polite')
+    expect(incorrect.text()).toContain('回答は不正解です')
+  })
+
+  it('共有answer fixtureをcorrectとincorrectの判定stateへ写像する', async () => {
+    const wrapper = mount(AnswerJudgeResult, {
+      props: answerJudgeResultFixtures.incorrect,
+    })
+
+    expect(wrapper.attributes('data-state')).toBe('incorrect')
+
+    await wrapper.setProps({ ...answerJudgeResultFixtures.correct })
+
+    expect(wrapper.attributes('data-state')).toBe('correct')
+  })
+})
diff --git a/client/src/components/room/__tests__/AnswerPanel.spec.ts b/client/src/components/room/__tests__/AnswerPanel.spec.ts
new file mode 100644
index 0000000..9cc4e63
--- /dev/null
+++ b/client/src/components/room/__tests__/AnswerPanel.spec.ts
@@ -0,0 +1,154 @@
+import { mount } from '@vue/test-utils'
+import { describe, expect, it } from 'vitest'
+
+import AnswerPanel from '../AnswerPanel.vue'
+import { answerPanelFixture } from '../AnswerPanel.fixture'
+
+const defaultProps = {
+  maxLength: answerPanelFixture.maxLength,
+  pending: false,
+  disabled: false,
+}
+
+describe('AnswerPanel', () => {
+  it('always renders an accessible input with the fixture maximum length', () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+    const textarea = wrapper.get('textarea[name="answer"]')
+    const label = wrapper.get('label')
+
+    expect(wrapper.get('section').attributes('id')).toBe('answer-panel')
+    expect(label.attributes('for')).toBe(textarea.attributes('id'))
+    expect(textarea.attributes('maxlength')).toBe(String(answerPanelFixture.maxLength))
+    expect(wrapper.text()).toContain(`最大${answerPanelFixture.maxLength}文字`)
+  })
+
+  it('emits the unchanged fixture answer exactly once through form submission', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+
+    await wrapper.get('textarea').setValue(answerPanelFixture.submittedAnswer)
+    await wrapper.get('form').trigger('submit')
+
+    expect(wrapper.emitted('submit')).toEqual([[answerPanelFixture.submittedAnswer]])
+  })
+
+  it('emits the answer exactly once when the submit button is clicked', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps, attachTo: document.body })
+    const submitButton = wrapper.get<HTMLButtonElement>('button[type="submit"]')
+
+    await wrapper.get('textarea').setValue(answerPanelFixture.submittedAnswer)
+    submitButton.element.click()
+    await wrapper.vm.$nextTick()
+
+    expect(wrapper.emitted('submit')).toEqual([[answerPanelFixture.submittedAnswer]])
+
+    wrapper.unmount()
+  })
+
+  it('preserves whitespace and allows an empty answer defined by the transport schema', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+    const textarea = wrapper.get('textarea')
+
+    await textarea.setValue('  answer\n')
+    await wrapper.get('form').trigger('submit')
+    await textarea.setValue('')
+    await wrapper.get('form').trigger('submit')
+
+    expect(wrapper.emitted('submit')).toEqual([['  answer\n'], ['']])
+  })
+
+  it('submits once on Enter and ignores repeated Enter presses', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+    const textarea = wrapper.get('textarea')
+
+    await textarea.setValue(answerPanelFixture.submittedAnswer)
+    const enter = new KeyboardEvent('keydown', {
+      key: 'Enter',
+      bubbles: true,
+      cancelable: true,
+    })
+    const repeatedEnter = new KeyboardEvent('keydown', {
+      key: 'Enter',
+      repeat: true,
+      bubbles: true,
+      cancelable: true,
+    })
+    textarea.element.dispatchEvent(enter)
+    textarea.element.dispatchEvent(repeatedEnter)
+
+    expect(wrapper.emitted('submit')).toEqual([[answerPanelFixture.submittedAnswer]])
+    expect(enter.defaultPrevented).toBe(true)
+    expect(repeatedEnter.defaultPrevented).toBe(true)
+  })
+
+  it('does not submit on Shift+Enter or while an IME composition is active', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+    const textarea = wrapper.get('textarea')
+
+    await textarea.setValue(answerPanelFixture.submittedAnswer)
+    const shiftedEnter = new KeyboardEvent('keydown', {
+      key: 'Enter',
+      shiftKey: true,
+      bubbles: true,
+      cancelable: true,
+    })
+    const composingEnter = new KeyboardEvent('keydown', {
+      key: 'Enter',
+      isComposing: true,
+      bubbles: true,
+      cancelable: true,
+    })
+    textarea.element.dispatchEvent(shiftedEnter)
+    textarea.element.dispatchEvent(composingEnter)
+
+    expect(wrapper.emitted('submit')).toBeUndefined()
+    expect(shiftedEnter.defaultPrevented).toBe(false)
+    expect(composingEnter.defaultPrevented).toBe(false)
+  })
+
+  it.each([
+    { pending: true, disabled: false },
+    { pending: false, disabled: true },
+  ])('blocks input and submission while unavailable: %o', async (props) => {
+    const wrapper = mount(AnswerPanel, {
+      props: { ...defaultProps, ...props },
+    })
+    const textarea = wrapper.get('textarea')
+
+    expect(textarea.attributes('disabled')).toBeDefined()
+    expect(wrapper.get('button[type="submit"]').attributes('disabled')).toBeDefined()
+
+    await wrapper.get('form').trigger('submit')
+    await textarea.trigger('keydown', { key: 'Enter' })
+
+    expect(wrapper.emitted('submit')).toBeUndefined()
+  })
+
+  it('keeps the draft while pending changes', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+
+    await wrapper.get('textarea').setValue(answerPanelFixture.submittedAnswer)
+    await wrapper.setProps({ pending: true })
+    expect(wrapper.get('textarea').element.value).toBe(answerPanelFixture.submittedAnswer)
+
+    await wrapper.setProps({ pending: false })
+
+    expect(wrapper.get('textarea').element.value).toBe(answerPanelFixture.submittedAnswer)
+  })
+
+  it('accepts the exact maximum and rejects a programmatic value over it', async () => {
+    const wrapper = mount(AnswerPanel, { props: defaultProps })
+    const textarea = wrapper.get('textarea')
+
+    const maximumAnswer = 'x'.repeat(answerPanelFixture.maxLength)
+    await textarea.setValue(maximumAnswer)
+    await wrapper.get('form').trigger('submit')
+
+    expect(wrapper.emitted('submit')).toEqual([[maximumAnswer]])
+
+    await textarea.setValue('x'.repeat(answerPanelFixture.maxLength + 1))
+    await wrapper.get('form').trigger('submit')
+
+    expect(wrapper.emitted('submit')).toEqual([[maximumAnswer]])
+    expect(wrapper.get('button[type="submit"]').attributes('disabled')).toBeDefined()
+  })
+})