diff --git a/packages/backend/src/core/VideoProcessingService.ts b/packages/backend/src/core/VideoProcessingService.ts
index 2807960cb..ea5701dec 100644
--- a/packages/backend/src/core/VideoProcessingService.ts
+++ b/packages/backend/src/core/VideoProcessingService.ts
@@ -35,9 +35,8 @@ export class VideoProcessingService {
 						timestamps: ['5%'],
 					});
 			});
-	
-			// JPEGに変換 (Webpでもいいが、MastodonはWebpをサポートせず表示できなくなる)
-			return await this.imageProcessingService.convertToJpeg(`${dir}/out.png`, 498, 280);
+
+			return await this.imageProcessingService.convertToWebp(`${dir}/out.png`, 498, 280);
 		} finally {
 			cleanup();
 		}