diff --git a/packages/backend/src/server/api/endpoints/ap/show.ts b/packages/backend/src/server/api/endpoints/ap/show.ts
index 4afed7dc5c..46df43325d 100644
--- a/packages/backend/src/server/api/endpoints/ap/show.ts
+++ b/packages/backend/src/server/api/endpoints/ap/show.ts
@@ -21,6 +21,10 @@ import { bindThis } from '@/decorators.js';
 import { ApiError } from '../../error.js';
 import { IdentifiableError } from '@/misc/identifiable-error.js';
 import { FetchAllowSoftFailMask } from '@/core/activitypub/misc/check-against-url.js';
+import * as Acct from '@/misc/acct.js';
+import { IsNull } from 'typeorm';
+import { DI } from '@/di-symbols.js';
+import type { NotesRepository, UsersRepository } from '@/models/_.js';
 
 export const meta = {
 	tags: ['federation'],
@@ -116,6 +120,9 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		private apDbResolverService: ApDbResolverService,
 		private apPersonService: ApPersonService,
 		private apNoteService: ApNoteService,
+
+		@Inject(DI.usersRepository)
+		private usersRepository: UsersRepository,
 	) {
 		super(meta, paramDef, async (ps, me) => {
 			const object = await this.fetchAny(ps.uri, me);
@@ -137,7 +144,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		}
 
 		let local = await this.mergePack(me, ...await Promise.all([
-			this.apDbResolverService.getUserFromApId(uri),
+			this.apDbResolverService.getUserFromApId(uri).then(async x => x ?? await this.getUserFromProfileUrl(uri)),
 			this.apDbResolverService.getNoteFromApId(uri),
 		]));
 		if (local != null) return local;
@@ -200,6 +207,30 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 		);
 	}
 
+	// To keep consistency with ap/show from external server,
+	// this function will handle `https://local.instance/@user`
+	// profile url to resolve user.
+	@bindThis
+	private async getUserFromProfileUrl(url: string): Promise<MiUser | null | undefined> {
+		if (!this.utilityService.isUriLocal(url)) {
+			return null;
+		}
+
+		const uri = new URL(url);
+		const pathComponents = uri.pathname.split('/').filter(Boolean);
+		if (pathComponents.length === 1 && pathComponents[0].startsWith('@')) {
+			const acct = Acct.parse(pathComponents[0]);
+
+			return await this.usersRepository.findOneBy({
+				usernameLower: acct.username.toLowerCase(),
+				host: acct.host ?? IsNull(),
+				isSuspended: false,
+			});
+		}
+
+		return null;
+	}
+
 	@bindThis
 	private async mergePack(me: MiLocalUser | null | undefined, user: MiUser | null | undefined, note: MiNote | null | undefined): Promise<SchemaType<typeof meta.res> | null> {
 		if (user != null) {