diff --git a/packages/backend/src/core/FileInfoService.ts b/packages/backend/src/core/FileInfoService.ts
index b8babcb3a7..82b731c609 100644
--- a/packages/backend/src/core/FileInfoService.ts
+++ b/packages/backend/src/core/FileInfoService.ts
@@ -317,6 +317,27 @@ export class FileInfoService {
 		return mime;
 	}
 
+	/**
+	 * ビデオファイルにビデオトラックがあるかどうかチェック
+	 * （ない場合：m4a, webmなど）
+	 */
+	@bindThis
+	private hasVideoTrackOnVideoFile(path: string): Promise<boolean> {
+		return new Promise((resolve, reject) => {
+			try {
+				FFmpeg.ffprobe(path, (err, metadata) => {
+					if (err) {
+						resolve(true);
+						return;
+					}
+					resolve(metadata.streams.some((stream) => stream.codec_type === 'video'));
+				});
+			} catch (e) {
+				resolve(true);
+			}
+		});
+	}
+
 	/**
 	 * Detect MIME Type and extension
 	 */
@@ -339,6 +360,26 @@ export class FileInfoService {
 				return TYPE_SVG;
 			}
 
+			if (type.mime.startsWith('video') && !(await this.hasVideoTrackOnVideoFile(path))) {
+				const newMime = `audio/${type.mime.split('/')[1]}`;
+				if (newMime === 'audio/mp4') {
+					return {
+						mime: 'audio/aac',
+						ext: 'm4a',
+					};
+				}
+				if (newMime === 'audio/webm') {
+					return {
+						mime: 'audio/webm',
+						ext: 'webm',
+					};
+				}
+				return {
+					mime: newMime,
+					ext: type.ext,
+				};
+			}
+
 			return {
 				mime: this.fixMime(type.mime),
 				ext: type.ext,
diff --git a/packages/backend/test/unit/FileInfoService.ts b/packages/backend/test/unit/FileInfoService.ts
index 2eec80d763..a33a6024f4 100644
--- a/packages/backend/test/unit/FileInfoService.ts
+++ b/packages/backend/test/unit/FileInfoService.ts
@@ -323,8 +323,6 @@ describe('FileInfoService', () => {
 			});
 		});
 
-		/*
-		 * video/webmとして検出されてしまう
 		test('WEBM AUDIO', async () => {
 			const path = `${resources}/kick_gaba7.webm`;
 			const info = await fileInfoService.getFileInfo(path, { skipSensitiveDetection: true }) as any;
@@ -344,6 +342,5 @@ describe('FileInfoService', () => {
 				},
 			});
 		});
-		 */
 	});
 });