diff --git a/packages/backend/src/server/api/endpoints/admin/avatar-decorations/create.ts b/packages/backend/src/server/api/endpoints/admin/avatar-decorations/create.ts
index fd213098188d..5e52d8e2b52a 100644
--- a/packages/backend/src/server/api/endpoints/admin/avatar-decorations/create.ts
+++ b/packages/backend/src/server/api/endpoints/admin/avatar-decorations/create.ts
@@ -6,6 +6,7 @@
 import { Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { AvatarDecorationService } from '@/core/AvatarDecorationService.js';
+import { DriveService } from '@/core/DriveService.js';
 
 export const meta = {
 	tags: ['admin'],
@@ -32,12 +33,19 @@ export const paramDef = {
 export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
 	constructor(
 		private avatarDecorationService: AvatarDecorationService,
+		private driveService: DriveService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			// システムユーザーとして再アップロード
+			const sysFileData = await this.driveService.uploadFromUrl({
+				url: ps.url,
+				user: null,
+				force: true,
+			});
 			await this.avatarDecorationService.create({
 				name: ps.name,
 				description: ps.description,
-				url: ps.url,
+				url: sysFileData.url,
 				roleIdsThatCanBeUsedThisDecoration: ps.roleIdsThatCanBeUsedThisDecoration,
 			}, me);
 		});
diff --git a/packages/backend/src/server/api/endpoints/admin/avatar-decorations/update.ts b/packages/backend/src/server/api/endpoints/admin/avatar-decorations/update.ts
index 34b3b5a11f50..9f12901d948a 100644
--- a/packages/backend/src/server/api/endpoints/admin/avatar-decorations/update.ts
+++ b/packages/backend/src/server/api/endpoints/admin/avatar-decorations/update.ts
@@ -7,6 +7,7 @@ import { Inject, Injectable } from '@nestjs/common';
 import { Endpoint } from '@/server/api/endpoint-base.js';
 import { DI } from '@/di-symbols.js';
 import { AvatarDecorationService } from '@/core/AvatarDecorationService.js';
+import { DriveService } from '@/core/DriveService.js';
 import { ApiError } from '../../../error.js';
 
 export const meta = {
@@ -38,12 +39,24 @@ export const paramDef = {
 export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-disable-line import/no-default-export
 	constructor(
 		private avatarDecorationService: AvatarDecorationService,
+		private driveService: DriveService,
 	) {
 		super(meta, paramDef, async (ps, me) => {
+			let fileUrl = ps.url;
+			// URLに変更があるか
+			if (typeof ps.url !== 'undefined' || typeof ps.url === 'string' ) {
+				// システムユーザーとして再アップロード
+				const sysFileData = await this.driveService.uploadFromUrl({
+					url: ps.url,
+					user: null,
+					force: true,
+				});
+				fileUrl = sysFileData.url;
+			}
 			await this.avatarDecorationService.update(ps.id, {
 				name: ps.name,
 				description: ps.description,
-				url: ps.url,
+				url: fileUrl,
 				roleIdsThatCanBeUsedThisDecoration: ps.roleIdsThatCanBeUsedThisDecoration,
 			}, me);
 		});