diff --git a/package.json b/package.json
index 274962c368..2ced82cd19 100644
--- a/package.json
+++ b/package.json
@@ -78,6 +78,7 @@
 		"@types/websocket": "0.0.37",
 		"accesses": "2.5.0",
 		"animejs": "2.2.0",
+		"autosize": "4.0.0",
 		"autwh": "0.0.1",
 		"bcryptjs": "2.4.3",
 		"body-parser": "1.18.2",
diff --git a/src/web/app/common/views/components/autocomplete.vue b/src/web/app/common/views/components/autocomplete.vue
index 1980804927..b068ecc4fa 100644
--- a/src/web/app/common/views/components/autocomplete.vue
+++ b/src/web/app/common/views/components/autocomplete.vue
@@ -22,7 +22,7 @@ import * as pictograph from 'pictograph';
 import contains from '../../../common/scripts/contains';
 
 export default Vue.extend({
-	props: ['type', 'q', 'textarea', 'complete', 'close'],
+	props: ['type', 'q', 'textarea', 'complete', 'close', 'x', 'y'],
 	data() {
 		return {
 			fetching: true,
@@ -37,6 +37,27 @@ export default Vue.extend({
 			return (this.$refs.suggests as Element).children;
 		}
 	},
+	updated() {
+		//#region 位置調整
+		const margin = 32;
+
+		if (this.x + this.$el.offsetWidth > window.innerWidth - margin) {
+			this.$el.style.left = (this.x - this.$el.offsetWidth) + 'px';
+			this.$el.style.marginLeft = '-16px';
+		} else {
+			this.$el.style.left = this.x + 'px';
+			this.$el.style.marginLeft = '0';
+		}
+
+		if (this.y + this.$el.offsetHeight > window.innerHeight - margin) {
+			this.$el.style.top = (this.y - this.$el.offsetHeight) + 'px';
+			this.$el.style.marginTop = '0';
+		} else {
+			this.$el.style.top = this.y + 'px';
+			this.$el.style.marginTop = 'calc(1em + 8px)';
+		}
+		//#endregion
+	},
 	mounted() {
 		this.textarea.addEventListener('keydown', this.onKeydown);
 
@@ -136,7 +157,7 @@ export default Vue.extend({
 
 <style lang="stylus" scoped>
 .mk-autocomplete
-	position absolute
+	position fixed
 	z-index 65535
 	margin-top calc(1em + 8px)
 	overflow hidden
diff --git a/src/web/app/common/views/components/messaging-room.form.vue b/src/web/app/common/views/components/messaging-room.form.vue
index aa07217b32..adc3372bed 100644
--- a/src/web/app/common/views/components/messaging-room.form.vue
+++ b/src/web/app/common/views/components/messaging-room.form.vue
@@ -1,6 +1,6 @@
 <template>
 <div class="mk-messaging-form">
-	<textarea v-model="text" @keypress="onKeypress" @paste="onPaste" placeholder="%i18n:common.input-message-here%" v-autocomplete></textarea>
+	<textarea v-model="text" ref="textarea" @keypress="onKeypress" @paste="onPaste" placeholder="%i18n:common.input-message-here%" v-autocomplete></textarea>
 	<div class="file" v-if="file">{{ file.name }}</div>
 	<mk-uploader ref="uploader"/>
 	<button class="send" @click="send" :disabled="sending" title="%i18n:common.send%">
@@ -18,6 +18,8 @@
 
 <script lang="ts">
 import Vue from 'vue';
+import * as autosize from 'autosize';
+
 export default Vue.extend({
 	props: ['user'],
 	data() {
@@ -27,6 +29,9 @@ export default Vue.extend({
 			sending: false
 		};
 	},
+	mounted() {
+		autosize(this.$refs.textarea);
+	},
 	methods: {
 		onPaste(e) {
 			const data = e.clipboardData;
@@ -93,6 +98,7 @@ export default Vue.extend({
 		height 64px
 		margin 0
 		padding 8px
+		resize none
 		font-size 1em
 		color #000
 		outline none
diff --git a/src/web/app/common/views/components/messaging-room.vue b/src/web/app/common/views/components/messaging-room.vue
index 7af6b3fae3..310b56f6fc 100644
--- a/src/web/app/common/views/components/messaging-room.vue
+++ b/src/web/app/common/views/components/messaging-room.vue
@@ -16,7 +16,6 @@
 	</div>
 	<footer>
 		<div ref="notifications" class="notifications"></div>
-		<div class="grippie" title="%i18n:common.tags.mk-messaging-room.resize-form%"></div>
 		<x-form :user="user"/>
 	</footer>
 </div>
@@ -316,16 +315,4 @@ export default Vue.extend({
 					line-height 32px
 					font-size 16px
 
-		> .grippie
-			height 10px
-			margin-top -10px
-			background transparent
-			cursor ns-resize
-
-			&:hover
-				//background rgba(0, 0, 0, 0.1)
-
-			&:active
-				//background rgba(0, 0, 0, 0.2)
-
 </style>
diff --git a/src/web/app/common/views/directives/autocomplete.ts b/src/web/app/common/views/directives/autocomplete.ts
index bd9c9cb611..4d6ba41df1 100644
--- a/src/web/app/common/views/directives/autocomplete.ts
+++ b/src/web/app/common/views/directives/autocomplete.ts
@@ -82,6 +82,15 @@ class Autocomplete {
 		// 既に開いているサジェストは閉じる
 		this.close();
 
+		//#region サジェストを表示すべき位置を計算
+		const caretPosition = getCaretCoordinates(this.textarea, this.textarea.selectionStart);
+
+		const rect = this.textarea.getBoundingClientRect();
+
+		const x = rect.left + caretPosition.left - this.textarea.scrollLeft;
+		const y = rect.top + caretPosition.top - this.textarea.scrollTop;
+		//#endregion
+
 		// サジェスト要素作成
 		this.suggestion = new MkAutocomplete({
 			propsData: {
@@ -89,22 +98,12 @@ class Autocomplete {
 				complete: this.complete,
 				close: this.close,
 				type: type,
-				q: q
+				q: q,
+				x,
+				y
 			}
 		}).$mount();
 
-		//#region サジェストを表示すべき位置を計算
-		const caretPosition = getCaretCoordinates(this.textarea, this.textarea.selectionStart);
-
-		const rect = this.textarea.getBoundingClientRect();
-
-		const x = rect.left + window.pageXOffset + caretPosition.left - this.textarea.scrollLeft;
-		const y = rect.top + window.pageYOffset + caretPosition.top - this.textarea.scrollTop;
-		//#endregion
-
-		this.suggestion.$el.style.left = x + 'px';
-		this.suggestion.$el.style.top = y + 'px';
-
 		// 要素追加
 		document.body.appendChild(this.suggestion.$el);
 	}