diff --git a/locales/index.d.ts b/locales/index.d.ts
index 75e1703b4a..8ad934f397 100644
--- a/locales/index.d.ts
+++ b/locales/index.d.ts
@@ -6686,6 +6686,10 @@ export interface Locale extends ILocale {
              * ノートのピン留めの最大数
              */
             "pinMax": string;
+            /**
+             * 一つのノートに対する最大リアクション数
+             */
+            "reactionsPerNoteLimit": string;
             /**
              * アンテナの作成可能数
              */
diff --git a/locales/ja-JP.yml b/locales/ja-JP.yml
index 98e3cbfa41..2d85f0840a 100644
--- a/locales/ja-JP.yml
+++ b/locales/ja-JP.yml
@@ -1728,6 +1728,7 @@ _role:
     alwaysMarkNsfw: "ファイルにNSFWを常に付与"
     canUpdateBioMedia: "アイコンとバナーの更新を許可"
     pinMax: "ノートのピン留めの最大数"
+    reactionsPerNoteLimit: "一つのノートに対する最大リアクション数"
     antennaMax: "アンテナの作成可能数"
     wordMuteMax: "ワードミュートの最大文字数"
     webhookMax: "Webhookの作成可能数"
diff --git a/packages/backend/migration/1721117896543-multiple-reactions.js b/packages/backend/migration/1721117896543-multiple-reactions.js
new file mode 100644
index 0000000000..d71128962e
--- /dev/null
+++ b/packages/backend/migration/1721117896543-multiple-reactions.js
@@ -0,0 +1,20 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export class MultipleReactions1721117896543 {
+	name = 'MultipleReactions1721117896543';
+
+	async up(queryRunner) {
+		await queryRunner.query('DROP INDEX "public"."IDX_ad0c221b25672daf2df320a817"');
+		await queryRunner.query('CREATE UNIQUE INDEX "IDX_a7751b74317122d11575bff31c" ON "note_reaction" ("userId", "noteId", "reaction") ');
+		await queryRunner.query('CREATE INDEX "IDX_ad0c221b25672daf2df320a817" ON "note_reaction" ("userId", "noteId") ');
+	}
+
+	async down(queryRunner) {
+		await queryRunner.query('DROP INDEX "public"."IDX_ad0c221b25672daf2df320a817"');
+		await queryRunner.query('DROP INDEX "public"."IDX_a7751b74317122d11575bff31c"');
+		await queryRunner.query('CREATE UNIQUE INDEX "IDX_ad0c221b25672daf2df320a817" ON "note_reaction" ("userId", "noteId") ');
+	}
+}
diff --git a/packages/backend/src/core/ReactionService.ts b/packages/backend/src/core/ReactionService.ts
index 371207c33a..9889d334ed 100644
--- a/packages/backend/src/core/ReactionService.ts
+++ b/packages/backend/src/core/ReactionService.ts
@@ -174,24 +174,12 @@ export class ReactionService {
 			reaction,
 		};
 
-		// Create reaction
 		try {
 			await this.noteReactionsRepository.insert(record);
 		} catch (e) {
 			if (isDuplicateKeyValueError(e)) {
-				const exists = await this.noteReactionsRepository.findOneByOrFail({
-					noteId: note.id,
-					userId: user.id,
-				});
-
-				if (exists.reaction !== reaction) {
-					// 別のリアクションがすでにされていたら置き換える
-					await this.delete(user, note);
-					await this.noteReactionsRepository.insert(record);
-				} else {
-					// 同じリアクションがすでにされていたらエラー
-					throw new IdentifiableError('51c42bb4-931a-456b-bff7-e5a8a70dd298');
-				}
+				// 同じリアクションがすでにされていたらエラー
+				throw new IdentifiableError('51c42bb4-931a-456b-bff7-e5a8a70dd298');
 			} else {
 				throw e;
 			}
@@ -286,11 +274,12 @@ export class ReactionService {
 	}
 
 	@bindThis
-	public async delete(user: { id: MiUser['id']; host: MiUser['host']; isBot: MiUser['isBot']; }, note: MiNote) {
+	public async delete(user: { id: MiUser['id']; host: MiUser['host']; isBot: MiUser['isBot']; }, note: MiNote, _reaction?: string | null) {
 		// if already unreacted
 		const exist = await this.noteReactionsRepository.findOneBy({
 			noteId: note.id,
 			userId: user.id,
+			reaction: _reaction ?? FALLBACK,
 		});
 
 		if (exist == null) {
diff --git a/packages/backend/src/core/RoleService.ts b/packages/backend/src/core/RoleService.ts
index 7966774673..f502c19aa6 100644
--- a/packages/backend/src/core/RoleService.ts
+++ b/packages/backend/src/core/RoleService.ts
@@ -49,6 +49,7 @@ export type RolePolicies = {
 	alwaysMarkNsfw: boolean;
 	canUpdateBioMedia: boolean;
 	pinLimit: number;
+	reactionsPerNoteLimit: number;
 	antennaLimit: number;
 	wordMuteLimit: number;
 	webhookLimit: number;
@@ -78,6 +79,7 @@ export const DEFAULT_POLICIES: RolePolicies = {
 	alwaysMarkNsfw: false,
 	canUpdateBioMedia: true,
 	pinLimit: 5,
+	reactionsPerNoteLimit: 1,
 	antennaLimit: 5,
 	wordMuteLimit: 200,
 	webhookLimit: 3,
@@ -380,6 +382,7 @@ export class RoleService implements OnApplicationShutdown, OnModuleInit {
 			alwaysMarkNsfw: calc('alwaysMarkNsfw', vs => vs.some(v => v === true)),
 			canUpdateBioMedia: calc('canUpdateBioMedia', vs => vs.some(v => v === true)),
 			pinLimit: calc('pinLimit', vs => Math.max(...vs)),
+			reactionsPerNoteLimit: calc('reactionsPerNoteLimit', vs => Math.max(...vs)),
 			antennaLimit: calc('antennaLimit', vs => Math.max(...vs)),
 			wordMuteLimit: calc('wordMuteLimit', vs => Math.max(...vs)),
 			webhookLimit: calc('webhookLimit', vs => Math.max(...vs)),
diff --git a/packages/backend/src/core/entities/NoteEntityService.ts b/packages/backend/src/core/entities/NoteEntityService.ts
index 2cd092231c..d1949d1432 100644
--- a/packages/backend/src/core/entities/NoteEntityService.ts
+++ b/packages/backend/src/core/entities/NoteEntityService.ts
@@ -170,10 +170,10 @@ export class NoteEntityService implements OnModuleInit {
 
 	@bindThis
 	public async populateMyReaction(note: { id: MiNote['id']; reactions: MiNote['reactions']; reactionAndUserPairCache?: MiNote['reactionAndUserPairCache']; }, meId: MiUser['id'], _hint_?: {
-		myReactions: Map<MiNote['id'], string | null>;
+		myReactionsMap: Map<MiNote['id'], string | null>;
 	}) {
-		if (_hint_?.myReactions) {
-			const reaction = _hint_.myReactions.get(note.id);
+		if (_hint_?.myReactionsMap) {
+			const reaction = _hint_.myReactionsMap.get(note.id);
 			if (reaction) {
 				return this.reactionService.convertLegacyReaction(reaction);
 			} else {
diff --git a/packages/backend/src/models/NoteReaction.ts b/packages/backend/src/models/NoteReaction.ts
index 42dfcaa9ad..366a4423f7 100644
--- a/packages/backend/src/models/NoteReaction.ts
+++ b/packages/backend/src/models/NoteReaction.ts
@@ -9,7 +9,8 @@ import { MiUser } from './User.js';
 import { MiNote } from './Note.js';
 
 @Entity('note_reaction')
-@Index(['userId', 'noteId'], { unique: true })
+@Index(['userId', 'noteId'])
+@Index(['userId', 'noteId', 'reaction'], { unique: true })
 export class MiNoteReaction {
 	@PrimaryColumn(id())
 	public id: string;
diff --git a/packages/backend/src/models/json-schema/role.ts b/packages/backend/src/models/json-schema/role.ts
index 7366f05356..5820aa32e3 100644
--- a/packages/backend/src/models/json-schema/role.ts
+++ b/packages/backend/src/models/json-schema/role.ts
@@ -236,6 +236,10 @@ export const packedRolePoliciesSchema = {
 			type: 'integer',
 			optional: false, nullable: false,
 		},
+		reactionsPerNoteLimit: {
+			type: 'integer',
+			optional: false, nullable: false,
+		},
 		antennaLimit: {
 			type: 'integer',
 			optional: false, nullable: false,
diff --git a/packages/frontend/src/const.ts b/packages/frontend/src/const.ts
index e135bc69a0..2bb534ccf2 100644
--- a/packages/frontend/src/const.ts
+++ b/packages/frontend/src/const.ts
@@ -89,6 +89,7 @@ export const ROLE_POLICIES = [
 	'alwaysMarkNsfw',
 	'canUpdateBioMedia',
 	'pinLimit',
+	'reactionsPerNoteLimit',
 	'antennaLimit',
 	'wordMuteLimit',
 	'webhookLimit',
diff --git a/packages/frontend/src/pages/admin/roles.editor.vue b/packages/frontend/src/pages/admin/roles.editor.vue
index 3e948abdf1..c298476a64 100644
--- a/packages/frontend/src/pages/admin/roles.editor.vue
+++ b/packages/frontend/src/pages/admin/roles.editor.vue
@@ -417,6 +417,25 @@ SPDX-License-Identifier: AGPL-3.0-only
 				</div>
 			</MkFolder>
 
+			<MkFolder v-if="matchQuery([i18n.ts._role._options.reactionsPerNoteLimit, 'reactionsPerNoteLimit'])">
+				<template #label>{{ i18n.ts._role._options.reactionsPerNoteLimit }}</template>
+				<template #suffix>
+					<span v-if="role.policies.reactionsPerNoteLimit.useDefault" :class="$style.useDefaultLabel">{{ i18n.ts._role.useBaseValue }}</span>
+					<span v-else>{{ role.policies.reactionsPerNoteLimit.value }}</span>
+					<span :class="$style.priorityIndicator"><i :class="getPriorityIcon(role.policies.reactionsPerNoteLimit)"></i></span>
+				</template>
+				<div class="_gaps">
+					<MkSwitch v-model="role.policies.reactionsPerNoteLimit.useDefault" :readonly="readonly">
+						<template #label>{{ i18n.ts._role.useBaseValue }}</template>
+					</MkSwitch>
+					<MkInput v-model="role.policies.reactionsPerNoteLimit.value" :disabled="role.policies.reactionsPerNoteLimit.useDefault" type="number" :readonly="readonly">
+					</MkInput>
+					<MkRange v-model="role.policies.reactionsPerNoteLimit.priority" :min="0" :max="2" :step="1" easing :textConverter="(v) => v === 0 ? i18n.ts._role._priority.low : v === 1 ? i18n.ts._role._priority.middle : v === 2 ? i18n.ts._role._priority.high : ''">
+						<template #label>{{ i18n.ts._role.priority }}</template>
+					</MkRange>
+				</div>
+			</MkFolder>
+
 			<MkFolder v-if="matchQuery([i18n.ts._role._options.antennaMax, 'antennaLimit'])">
 				<template #label>{{ i18n.ts._role._options.antennaMax }}</template>
 				<template #suffix>
diff --git a/packages/frontend/src/pages/admin/roles.vue b/packages/frontend/src/pages/admin/roles.vue
index 6fb950494b..d28cff295c 100644
--- a/packages/frontend/src/pages/admin/roles.vue
+++ b/packages/frontend/src/pages/admin/roles.vue
@@ -149,6 +149,13 @@ SPDX-License-Identifier: AGPL-3.0-only
 							</MkInput>
 						</MkFolder>
 
+						<MkFolder v-if="matchQuery([i18n.ts._role._options.reactionsPerNoteLimit, 'reactionsPerNoteLimit'])">
+							<template #label>{{ i18n.ts._role._options.reactionsPerNoteLimit }}</template>
+							<template #suffix>{{ policies.reactionsPerNoteLimit }}</template>
+							<MkInput v-model="policies.reactionsPerNoteLimit" type="number">
+							</MkInput>
+						</MkFolder>
+
 						<MkFolder v-if="matchQuery([i18n.ts._role._options.antennaMax, 'antennaLimit'])">
 							<template #label>{{ i18n.ts._role._options.antennaMax }}</template>
 							<template #suffix>{{ policies.antennaLimit }}</template>