diff --git a/cmd/file.go b/cmd/file.go
index 2635cadd1..3b4ac4c63 100644
--- a/cmd/file.go
+++ b/cmd/file.go
@@ -142,7 +142,7 @@ func genMissingThumbnails() *cobra.Command {
 	}
 	canGenerateWaveform := func(mimeType string) bool {
 		switch mimeType {
-		case "audio/mpeg", "audio/mp3", "audio/wav", "audio/x-wav":
+		case "audio/mpeg", "audio/mp3", "audio/wav", "audio/x-wav", "audio/m4a":
 			return true
 		default:
 			return false
@@ -245,6 +245,11 @@ func genMissingThumbnails() *cobra.Command {
 					if err != nil {
 						return fmt.Errorf("failed to generate thumbnail: %w", err)
 					}
+				case "audio/m4a":
+					r, err = ip.WaveformM4a(src, waveformWidth, waveformHeight)
+					if err != nil {
+						return fmt.Errorf("failed to generate thumbnail: %w", err)
+					}
 				default:
 					return nil
 				}
@@ -290,7 +295,7 @@ func genMissingThumbnails() *cobra.Command {
 					"AND f.mime IN ("+
 					// サムネイル生成が可能なmimeが変わったらここを変える
 					"'image/jpeg', 'image/png', 'image/gif', 'image/webp', "+
-					"'audio/mpeg', 'audio/mp3', 'audio/wav', 'audio/x-wav'"+
+					"'audio/mpeg', 'audio/mp3', 'audio/wav', 'audio/x-wav', 'audio/m4a'"+
 					") "+
 					"GROUP BY f.id, f.created_at "+
 					"HAVING COUNT(ft.file_id) = 0 "+
diff --git a/service/file/manager_impl.go b/service/file/manager_impl.go
index 00c9bf7e9..577761706 100644
--- a/service/file/manager_impl.go
+++ b/service/file/manager_impl.go
@@ -58,7 +58,7 @@ func (m *managerImpl) canGenerateThumbnail(mimeType string) bool {
 
 func (m *managerImpl) canGenerateWaveform(mimeType string) bool {
 	switch mimeType {
-	case "audio/mpeg", "audio/mp3", "audio/wav", "audio/x-wav":
+	case "audio/mpeg", "audio/mp3", "audio/wav", "audio/x-wav", "audio/m4a":
 		return true
 	default:
 		return false
@@ -146,7 +146,13 @@ func (m *managerImpl) Save(ctx context.Context, args SaveArgs) (model.File, erro
 			if err != nil {
 				m.l.Warn("failed to generate thumbnail", zap.Error(err), zap.Stringer("fid", f.ID))
 			}
+		case "audio/m4a":
+			r, err = m.ip.WaveformM4a(src, waveformWidth, waveformHeight)
+			if err != nil {
+				m.l.Warn("failed to generate thumbnail", zap.Error(err), zap.Stringer("fid", f.ID))
+			}
 		}
+		
 
 		if r != nil {
 			thumbnail := model.FileThumbnail{
diff --git a/service/file/manager_impl_test.go b/service/file/manager_impl_test.go
index d0fda17da..fcb0e3f0c 100644
--- a/service/file/manager_impl_test.go
+++ b/service/file/manager_impl_test.go
@@ -415,6 +415,69 @@ func TestManagerImpl_Save(t *testing.T) {
 			assert.EqualValues(t, "image/svg+xml", thumbs[0].Mime)
 		}
 	})
+	t.Run("audio with generating waveform (m4a, io.ReadSeeker)", func(t *testing.T) {
+		t.Parallel()
+		ctrl := gomock.NewController(t)
+		repo := mock_repository.NewMockFileRepository(ctrl)
+		fs := mock_storage.NewMockFileStorage(ctrl)
+		ip := mock_imaging.NewMockProcessor(ctrl)
+		fm := initFM(t, repo, fs, ip)
+
+		data := []byte("test text file")
+		hash := "7e6d5d7ae4965bfecc6d818f76eb832b"
+		args := SaveArgs{
+			FileName:  "dummy.m4a",
+			FileSize:  int64(len(data)),
+			MimeType:  "audio/m4a",
+			FileType:  model.FileTypeUserFile,
+			ChannelID: optional.From(uuid.NewV3(uuid.Nil, "c")),
+			Src:       bytes.NewReader(data),
+		}
+		waveform := bytes.NewBufferString("dummy svg file")
+
+		fs.EXPECT().
+			SaveByKey(gomock.Any(), gomock.Any(), args.FileName, args.MimeType, args.FileType).
+			Do(func(src io.Reader, _, _, _ string, _ model.FileType) {
+				_, _ = io.Copy(io.Discard, src)
+			}).
+			Return(nil).
+			Times(1)
+		fs.EXPECT().
+			SaveByKey(gomock.Any(), gomock.Any(), gomock.Any(), "image/svg+xml", model.FileTypeThumbnail).
+			DoAndReturn(func(src io.Reader, _, _, _ string, _ model.FileType) error {
+				_, _ = io.Copy(io.Discard, src)
+				return nil
+			}).
+			Times(1)
+		repo.EXPECT().
+			SaveFileMeta(gomock.Any(), gomock.Any(), []*model.FileACLEntry{{UserID: uuid.Nil, Allow: true}}).
+			Do(func(_ context.Context, meta *model.FileMeta, _ []*model.FileACLEntry) { meta.CreatedAt = time.Now() }).
+			Return(nil).
+			Times(1)
+		ip.EXPECT().
+			WaveformM4a(gomock.Any(), gomock.Any(), gomock.Any()).
+			Do(func(src io.ReadSeeker, _, _ int) { _, _ = io.Copy(io.Discard, src) }).
+			Return(waveform, nil).
+			Times(1)
+
+		result, err := fm.Save(context.TODO(), args)
+		if assert.NoError(t, err) {
+			assert.NotEmpty(t, result.GetID())
+			assert.EqualValues(t, args.FileName, result.GetFileName())
+			assert.EqualValues(t, args.FileSize, result.GetFileSize())
+			assert.EqualValues(t, args.MimeType, result.GetMIMEType())
+			assert.EqualValues(t, args.FileType, result.GetFileType())
+			assert.EqualValues(t, args.ChannelID, result.GetUploadChannelID())
+			assert.EqualValues(t, args.CreatorID, result.GetCreatorID())
+			assert.EqualValues(t, hash, result.GetMD5Hash())
+			assert.EqualValues(t, false, result.IsAnimatedImage())
+			assert.NotEmpty(t, result.GetCreatedAt())
+			thumbs := result.GetThumbnails()
+			assert.EqualValues(t, 1, len(thumbs))
+			assert.EqualValues(t, model.ThumbnailTypeWaveform, thumbs[0].Type)
+			assert.EqualValues(t, "image/svg+xml", thumbs[0].Mime)
+		}
+	})
 }
 
 func TestManagerImpl_Get(t *testing.T) {
diff --git a/service/imaging/mock_imaging/mock_processor.go b/service/imaging/mock_imaging/mock_processor.go
index d5c06e3b8..52fd08ee4 100644
--- a/service/imaging/mock_imaging/mock_processor.go
+++ b/service/imaging/mock_imaging/mock_processor.go
@@ -110,3 +110,18 @@ func (mr *MockProcessorMockRecorder) WaveformWav(src, width, height interface{})
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WaveformWav", reflect.TypeOf((*MockProcessor)(nil).WaveformWav), src, width, height)
 }
+
+// WaveformM4a mocks base method.
+func (m *MockProcessor) WaveformM4a(src io.ReadSeeker, width, height int) (io.Reader, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "WaveformM4a", src, width, height)
+	ret0, _ := ret[0].(io.Reader)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// WaveformM4a indicates an expected call of WaveformM4a.
+func (mr *MockProcessorMockRecorder) WaveformM4a(src, width, height interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WaveformM4a", reflect.TypeOf((*MockProcessor)(nil).WaveformM4a), src, width, height)
+}
\ No newline at end of file
diff --git a/service/imaging/processor.go b/service/imaging/processor.go
index e01416596..761f0bf3e 100644
--- a/service/imaging/processor.go
+++ b/service/imaging/processor.go
@@ -13,4 +13,5 @@ type Processor interface {
 	FitAnimationGIF(src io.Reader, width, height int) (*bytes.Reader, error)
 	WaveformMp3(src io.ReadSeeker, width, height int) (io.Reader, error)
 	WaveformWav(src io.ReadSeeker, width, height int) (io.Reader, error)
+	WaveformM4a(src io.ReadSeeker, width, height int) (io.Reader, error)
 }
diff --git a/service/imaging/processor_default.go b/service/imaging/processor_default.go
index 0a37fe91e..6f2d29f43 100644
--- a/service/imaging/processor_default.go
+++ b/service/imaging/processor_default.go
@@ -262,3 +262,11 @@ func (p *defaultProcessor) WaveformWav(src io.ReadSeeker, width, height int) (io
 		Height:     height,
 	})
 }
+func (p *defaultProcessor) WaveformM4a(src io.ReadSeeker, width, height int) (io.Reader, error) {
+	d := m4a.NewDecoder(src)
+	return waveform.OutputWaveformImageM4a(d, &waveform.Option{
+		Resolution: width / 5,
+		Width:      width,
+		Height:     height,
+	})
+}
\ No newline at end of file
diff --git a/service/qall/soundboard_impl.go b/service/qall/soundboard_impl.go
index 441785625..28b469b6a 100644
--- a/service/qall/soundboard_impl.go
+++ b/service/qall/soundboard_impl.go
@@ -115,7 +115,7 @@ func (m *soundboardManager) DeleteSoundboardItem(ctx context.Context, soundID uu
 }
 
 // checkAudioDuration は拡張子(ext)に基づいて対応ライブラリを使い、秒数をチェックする
-// mp3 / wav / ogg に対応し、それ以外は "we only support mp3, wav, ogg" エラー
+// mp3 / wav / ogg / m4a に対応し、それ以外は "we only support mp3, wav, ogg, m4a" エラー
 func checkAudioDuration(fileBytes []byte, contentType string, maxSeconds float64) error {
 	switch contentType {
 	case "audio/mpeg", "audio/mp3":
@@ -147,9 +147,18 @@ func checkAudioDuration(fileBytes []byte, contentType string, maxSeconds float64
 			return fmt.Errorf("audio is too long (%.1f sec). Must be <= %.0f", dur, maxSeconds)
 		}
 		return nil
+	case "audio/m4a":
+		dur, err := getM4aDuration(fileBytes)
+		if err != nil {
+			return fmt.Errorf("m4a decode error: %w", err)
+		}
+		if dur > maxSeconds {
+			return fmt.Errorf("audio is too long (%.1f sec). Must be <= %.0f", dur, maxSeconds)
+		}
+		return nil
 
 	default:
-		return errors.New("we only support .mp3, .wav, .ogg")
+		return errors.New("we only support .mp3, .wav, .ogg, .m4a")
 	}
 }
 
@@ -206,3 +215,23 @@ func getOggDuration(data []byte) (float64, error) {
 	seconds := sampleCount / sampleRate
 	return seconds, nil
 }
+
+// getM4aDuration returns duration in seconds for M4A
+func getM4aDuration(data []byte) (float64, error) {
+	r := bytes.NewReader(data)
+	m4aDecoder := m4a.NewDecoder(r)
+	buf, err := m4aDecoder.FullPCMBuffer()
+	if err != nil {
+		return 0, err
+	}
+	if buf == nil || buf.Format == nil {
+		return 0, errors.New("invalid m4a format or buffer")
+	}
+	sampleRate := float64(buf.Format.SampleRate)
+	sampleCount := float64(len(buf.Data)) // PCMBufferのサンプル数
+	if sampleRate <= 0 {
+		return 0, errors.New("invalid m4a sample rate")
+	}
+	seconds := sampleCount / sampleRate
+	return seconds, nil
+}
\ No newline at end of file