diff --git a/client/src/App.vue b/client/src/App.vue
index 1414b95..ef82415 100644
--- a/client/src/App.vue
+++ b/client/src/App.vue
@@ -8,9 +8,9 @@ const actions = ['Save changes', 'Duplicate', 'Archive']
 
 <template>
   <main class="app-shell">
-    <section class="hero" aria-labelledby="app-title">
+    <section class="hero" aria-labelledby="app-name">
       <p class="eyebrow">1Monthon 2026 · Team 11</p>
-      <h1 id="app-title">Frontend is ready.</h1>
+      <h1 id="app-name">Frontend is ready.</h1>
       <p class="description">
         Vue と Rust server をつなぐための、シンプルな開発環境をセットアップしました。
       </p>
diff --git a/client/src/RoomCard.story.vue b/client/src/RoomCard.story.vue
new file mode 100644
index 0000000..ea17abb
--- /dev/null
+++ b/client/src/RoomCard.story.vue
@@ -0,0 +1,27 @@
+<script setup lang="ts">
+import RoomCard from './RoomCard.vue'
+
+const roomFixture = {
+  room_id: '1411824c-d357-4941-af76-c76cb827dda6',
+  number: 1,
+  name: '最初の部屋',
+  genre: 'logic',
+  description: '動作確認用の問題セットです',
+}
+</script>
+
+<template>
+  <Story title="RoomCard">
+    <Variant title="Closed">
+      <div style="width: 24rem; padding: 2rem">
+        <RoomCard :room="roomFixture" />
+      </div>
+    </Variant>
+
+    <Variant title="Open">
+      <div style="width: 24rem; padding: 2rem">
+        <RoomCard :room="roomFixture" default-open />
+      </div>
+    </Variant>
+  </Story>
+</template>
diff --git a/client/src/RoomCard.vue b/client/src/RoomCard.vue
new file mode 100644
index 0000000..546c6dd
--- /dev/null
+++ b/client/src/RoomCard.vue
@@ -0,0 +1,174 @@
+<script setup lang="ts">
+import { Disclosure, DisclosureButton, DisclosurePanel } from '@headlessui/vue'
+
+export interface Room {
+  room_id: string
+  number: number
+  name: string
+  genre: string
+  description: string
+}
+
+withDefaults(
+  defineProps<{
+    room: Room
+    defaultOpen?: boolean
+    starting?: boolean
+  }>(),
+  {
+    defaultOpen: false,
+    starting: false,
+  },
+)
+
+const emit = defineEmits<{
+  start: [roomId: string]
+}>()
+</script>
+
+<template>
+  <Disclosure v-slot="{ open }" as="article" class="room-card" :default-open="defaultOpen">
+    <DisclosureButton class="room-card__header" type="button">
+      <span class="room-card__number" aria-hidden="true">{{ room.number }}</span>
+      <span class="room-card__heading">
+        <span class="room-card__genre">{{ room.genre }}</span>
+        <span class="room-card__title">{{ room.name }}</span>
+      </span>
+      <span class="room-card__toggle" aria-hidden="true" :data-open="open">
+        <img
+          src="@/assets/icon/keyboard_arrow_down_24dp_1F1F1F_FILL0_wght400_GRAD0_opsz24.svg"
+          alt=""
+          aria-hidden="true"
+        />
+      </span>
+    </DisclosureButton>
+
+    <DisclosurePanel class="room-card__body">
+      <p class="room-card__description">{{ room.description }}</p>
+      <button
+        class="room-card__start"
+        type="button"
+        :disabled="starting"
+        @click="emit('start', room.room_id)"
+      >
+        {{ starting ? '開始しています…' : '開始する' }}
+      </button>
+    </DisclosurePanel>
+  </Disclosure>
+</template>
+
+<style scoped>
+.room-card {
+  width: 100%;
+  overflow: hidden;
+  border: 1px solid #d8e1ee;
+  border-radius: 1.25rem;
+  color: #121a2a;
+  background: #fff;
+  box-shadow: 0 0.25rem 1.75rem rgb(21 34 56 / 12%);
+  backdrop-filter: blur(1rem);
+}
+
+.room-card__header {
+  display: flex;
+  width: 100%;
+  align-items: center;
+  justify-content: flex-start;
+  gap: 1rem;
+  padding: 1.25rem 1.5rem;
+  border: 0;
+  color: inherit;
+  background: transparent;
+  cursor: pointer;
+  text-align: left;
+}
+
+.room-card__heading {
+  display: grid;
+  flex: 1;
+  gap: 0.2rem;
+}
+
+.room-card__genre {
+  color: hsl(244, 60%, 64%);
+  font-size: 0.9rem;
+  font-weight: 700;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+}
+
+.room-card__header:hover {
+  background: #f5f8fc;
+}
+
+.room-card__header:focus-visible {
+  outline: 2px solid #5eead4;
+  outline-offset: -2px;
+}
+
+.room-card__title {
+  font-size: 2rem;
+  font-weight: 700;
+  letter-spacing: -0.01em;
+}
+
+.room-card__toggle {
+  color: #65758d;
+  font-size: 1.25rem;
+  font-variation-settings:
+    'FILL' 0,
+    'wght' 400,
+    'GRAD' 0,
+    'opsz' 24;
+  line-height: 1;
+  transition: transform 160ms ease;
+}
+
+.room-card__toggle[data-open='true'] {
+  transform: rotate(180deg);
+}
+
+.room-card__body {
+  display: grid;
+  gap: 1.25rem;
+  padding: 1.25rem 1.5rem 1.5rem;
+  border-top: 1px solid #e5eaf2;
+}
+
+.room-card__description {
+  margin: 0;
+  color: #65758d;
+  line-height: 1.7;
+}
+
+.room-card__start {
+  justify-self: end;
+  padding: 0.7rem 1.1rem;
+  border: 0;
+  border-radius: 0.7rem;
+  color: #07111f;
+  background: hsl(171 30% 78%);
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.room-card__start:hover:not(:disabled) {
+  background: hsl(171 35% 70%);
+}
+
+.room-card__start:focus-visible {
+  outline: 2px solid hsl(171 45% 42%);
+  outline-offset: 3px;
+}
+
+.room-card__start:disabled {
+  cursor: wait;
+  opacity: 0.6;
+}
+
+.room-card__number {
+  font-size: 3rem;
+  font-weight: 700;
+  letter-spacing: -0.01em;
+}
+</style>
diff --git a/client/src/__tests__/RoomCard.spec.ts b/client/src/__tests__/RoomCard.spec.ts
new file mode 100644
index 0000000..8349910
--- /dev/null
+++ b/client/src/__tests__/RoomCard.spec.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest'
+import { mount } from '@vue/test-utils'
+
+import RoomCard from '../RoomCard.vue'
+
+const room = {
+  room_id: '1411824c-d357-4941-af76-c76cb827dda6',
+  number: 1,
+  name: '最初の部屋',
+  genre: 'logic',
+  description: '動作確認用の問題セットです',
+}
+
+describe('RoomCard', () => {
+  it('renders the collapsed card shell', () => {
+    const wrapper = mount(RoomCard, { props: { room } })
+
+    expect(wrapper.get('article').classes()).toContain('room-card')
+    expect(wrapper.get('.room-card__header').text()).toContain(room.name)
+    expect(wrapper.find('.room-card__body').exists()).toBe(false)
+  })
+
+  it('opens and closes its content from the header button', async () => {
+    const wrapper = mount(RoomCard, { props: { room } })
+
+    await wrapper.get('.room-card__header').trigger('click')
+    expect(wrapper.get('.room-card__description').text()).toBe(room.description)
+
+    await wrapper.get('.room-card__header').trigger('click')
+    expect(wrapper.find('.room-card__body').exists()).toBe(false)
+  })
+
+  it('emits the room ID from the start button', async () => {
+    const wrapper = mount(RoomCard, { props: { room, defaultOpen: true } })
+
+    await wrapper.get('.room-card__start').trigger('click')
+
+    expect(wrapper.emitted('start')).toEqual([[room.room_id]])
+  })
+})
diff --git a/client/src/assets/icon/keyboard_arrow_down_24dp_1F1F1F_FILL0_wght400_GRAD0_opsz24.svg b/client/src/assets/icon/keyboard_arrow_down_24dp_1F1F1F_FILL0_wght400_GRAD0_opsz24.svg
new file mode 100644
index 0000000..24729e0
--- /dev/null
+++ b/client/src/assets/icon/keyboard_arrow_down_24dp_1F1F1F_FILL0_wght400_GRAD0_opsz24.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" height="24px" viewBox="0 -960 960 960" width="24px" fill="#1f1f1f"><path d="M480-344 240-584l56-56 184 184 184-184 56 56-240 240Z"/></svg>
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