diff --git a/src/components/event/EventFormBase.vue b/src/components/event/EventFormBase.vue
index 3933b7a0..8d6f53fa 100644
--- a/src/components/event/EventFormBase.vue
+++ b/src/components/event/EventFormBase.vue
@@ -75,6 +75,10 @@ import EventFormSummary, {
 } from '@/components/event/EventFormSummary.vue'
 import FormNextButton from '@/components/shared/FormNextButton.vue'
 import FormBackButton from '@/components/shared/FormBackButton.vue'
+import { useDraftConfirmer } from '@/workers/draftConfirmer'
+import { removeDraftConfirmer } from '@/workers/draftConfirmer'
+import router from '@/router'
+import { Route } from 'vue-router'
 
 export type EventInput = EventInputContent &
   (
@@ -115,6 +119,10 @@ export default class EventFormBase extends Vue {
 
   instant: boolean = null!
 
+  originalSummary: EventSummary = null!
+
+  beforeEachControl: (() => void) | null = null
+
   created() {
     this.content = {
       name: this.event?.name ?? '',
@@ -197,8 +205,107 @@ export default class EventFormBase extends Vue {
     }
   }
 
+  isChanged(): boolean {
+    if (this.summary && this.originalSummary) {
+      return (
+        JSON.stringify(this.summary) !== JSON.stringify(this.originalSummary)
+      )
+    }
+    return false
+  }
+
+  cleanupContent(): void {
+    this.summary.name = ''
+    this.summary.description = ''
+    this.summary.tags = []
+    this.summary.groupName = ''
+    this.summary.place = ''
+    this.summary.timeStart = ''
+    this.summary.timeEnd = ''
+    this.summary.open = false
+    this.summary.sharedRoom = true
+  }
+
+  isEventNewOrEdit(): boolean {
+    const currentRoute: Route = this.$route
+    return currentRoute.name === 'EventNew'
+  }
+
+  beforLeaveGuardinEventEdit = (to, from, next) => {
+    if (from.name !== 'EventEdit') {
+      return next()
+    }
+
+    if (!this.isChanged()) {
+      return next()
+    }
+
+    if (
+      confirm(
+        '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+      )
+    ) {
+      removeDraftConfirmer()
+      this.cleanupContent()
+      return next()
+    }
+
+    return next(false)
+  }
+
+  beforLeaveGuardinEventNew = (to, from, next) => {
+    if (from.name !== 'EventNew' || !this.isChanged()) {
+      return next()
+    }
+
+    if (
+      confirm(
+        '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+      )
+    ) {
+      removeDraftConfirmer()
+      this.cleanupContent()
+      return next()
+    }
+
+    return next(false)
+  }
+
+  mounted() {
+    this.$watch(
+      'summary',
+      () => {
+        if (this.isChanged()) {
+          useDraftConfirmer()
+        } else {
+          removeDraftConfirmer()
+        }
+      },
+      { deep: true }
+    )
+    if (this.isEventNewOrEdit()) {
+      this.beforeEachControl = router.beforeEach(this.beforLeaveGuardinEventNew)
+    } else {
+      this.beforeEachControl = router.beforeEach(
+        this.beforLeaveGuardinEventEdit
+      )
+    }
+    this.originalSummary = JSON.parse(JSON.stringify(this.summary))
+  }
+
+  beforeDestroy() {
+    if (this.beforeEachControl) {
+      this.beforeEachControl()
+    }
+  }
+
   @Emit()
   submit(): EventOutput {
+    removeDraftConfirmer()
+    this.cleanupContent()
+    if (this.beforeEachControl) {
+      this.beforeEachControl()
+    }
     return {
       ...this.content,
       group: this.content.group!,
diff --git a/src/components/main/SidebarFooter.vue b/src/components/main/SidebarFooter.vue
index b6fc9e1f..f4bbe878 100644
--- a/src/components/main/SidebarFooter.vue
+++ b/src/components/main/SidebarFooter.vue
@@ -59,6 +59,8 @@
 
 <script lang="ts">
 import { isValidVerifiedroomData } from '@/workers/isValidVerifiedroomData'
+import { useDraftConfirmer } from '@/workers/draftConfirmer'
+import { removeDraftConfirmer } from '@/workers/draftConfirmer'
 import { baseURL } from '@/workers/api'
 
 export default {
@@ -75,21 +77,42 @@ export default {
       return this.$store.direct.state.me?.privileged ?? false
     },
   },
+  mounted: function () {
+    this.$watch('inputData', newVal => {
+      if (newVal !== '') {
+        useDraftConfirmer()
+      } else {
+        removeDraftConfirmer()
+      }
+    })
+  },
   methods: {
     showModal() {
       this.isVisible = true
     },
     hideModal() {
-      this.isVisible = false
-      this.showError = false
-      this.inputData = ''
+      if (this.inputData) {
+        if (
+          confirm(
+            '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+          )
+        ) {
+          this.isVisible = false
+          this.showError = false
+          this.inputData = ''
+        }
+        return
+      } else {
+        this.isVisible = false
+        this.showError = false
+        this.inputData = ''
+      }
     },
     async saveData() {
       if (isValidVerifiedroomData(this.inputData)) {
         this.showError = false
         try {
           await fetch(`${baseURL}/rooms/all`, {
-            //開発環境url
             method: 'POST',
             credentials: 'include',
             headers: {
diff --git a/src/pages/GroupEdit.vue b/src/pages/GroupEdit.vue
index d9f25157..91b72c20 100644
--- a/src/pages/GroupEdit.vue
+++ b/src/pages/GroupEdit.vue
@@ -56,6 +56,9 @@ import FormBackButton from '@/components/shared/FormBackButton.vue'
 import ProgressCircular from '@/components/shared/ProgressCircular.vue'
 import LoadFailedText from '@/components/shared/LoadFailedText.vue'
 import api, { RequestGroup } from '@/api'
+import router from '@/router'
+import { useDraftConfirmer } from '@/workers/draftConfirmer'
+import { removeDraftConfirmer } from '@/workers/draftConfirmer'
 
 @Component({
   components: {
@@ -74,6 +77,8 @@ export default class GroupEdit extends Vue {
   step = 1
 
   group: RequestGroup | null = null
+  originalGroup: RequestGroup | null = null
+  beforeEachControl: (() => void) | null = null
 
   get groupId() {
     return this.$route.params.id
@@ -84,6 +89,7 @@ export default class GroupEdit extends Vue {
     try {
       const group = await api.groups.getGroup({ groupID: this.groupId })
       this.group = group
+      this.originalGroup = JSON.parse(JSON.stringify(group))
       this.canEdit =
         !group.isTraQGroup && !!this.me && group.admins.includes(this.me)
       this.status = 'loaded'
@@ -92,6 +98,35 @@ export default class GroupEdit extends Vue {
     }
   }
 
+  isChanged(): boolean {
+    if (this.group && this.originalGroup) {
+      return JSON.stringify(this.group) !== JSON.stringify(this.originalGroup)
+    }
+    return false
+  }
+
+  cleanupContent(): void {
+    this.group = this.originalGroup
+  }
+
+  beforeLeaveGuard = (to, from, next) => {
+    if (from.path !== `/groups/edit/${this.groupId}` || !this.isChanged()) {
+      return next()
+    }
+
+    if (
+      confirm(
+        '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+      )
+    ) {
+      removeDraftConfirmer()
+      this.cleanupContent()
+      return next()
+    }
+
+    return next(false)
+  }
+
   async submitGroup() {
     if (!this.group) return
     try {
@@ -99,6 +134,8 @@ export default class GroupEdit extends Vue {
         groupID: this.groupId,
         requestGroup: this.group,
       })
+      removeDraftConfirmer()
+      this.cleanupContent()
       this.$router.push(`/groups/${this.groupId}`)
     } catch (__) {
       alert('Failed to submit...')
@@ -125,9 +162,32 @@ export default class GroupEdit extends Vue {
     if (!confirmed) return
     try {
       await api.groups.deleteGroup({ groupID: this.groupId })
-      this.$router.push('/')
-    } catch (__) {
-      alert('Failed to submit...')
+      removeDraftConfirmer()
+      this.cleanupContent()
+      this.$router.push('/groups')
+    } catch (error) {
+      alert('Failed to delete...')
+    }
+  }
+
+  mounted() {
+    this.$watch(
+      'group',
+      () => {
+        if (this.isChanged()) {
+          useDraftConfirmer()
+        } else {
+          removeDraftConfirmer()
+        }
+      },
+      { deep: true }
+    )
+    this.beforeEachControl = router.beforeEach(this.beforeLeaveGuard)
+  }
+
+  beforeDestroy() {
+    if (this.beforeEachControl) {
+      this.beforeEachControl()
     }
   }
 
diff --git a/src/pages/GroupNew.vue b/src/pages/GroupNew.vue
index 83245a9f..6f9a0adb 100644
--- a/src/pages/GroupNew.vue
+++ b/src/pages/GroupNew.vue
@@ -35,6 +35,9 @@ import GroupFormSummary from '@/components/group/GroupFormSummary.vue'
 import FormNextButton from '@/components/shared/FormNextButton.vue'
 import FormBackButton from '@/components/shared/FormBackButton.vue'
 import api, { RequestGroup } from '@/api'
+import { useDraftConfirmer } from '@/workers/draftConfirmer'
+import { removeDraftConfirmer } from '@/workers/draftConfirmer'
+import router from '@/router'
 
 @Component({
   components: {
@@ -48,6 +51,8 @@ export default class GroupNew extends Vue {
   valid = false
   step = 1
 
+  beforeEachControl: (() => void) | null = null
+
   group: RequestGroup = {
     name: '',
     description: '',
@@ -60,6 +65,57 @@ export default class GroupNew extends Vue {
       : [],
   }
 
+  hasContent(): boolean {
+    return (
+      this.group.name !== '' || this.group.description !== '' || this.group.open
+    )
+  }
+
+  cleanupContent(): void {
+    this.group.name = ''
+    this.group.description = ''
+    this.group.open = false
+  }
+
+  beforeLeaveGuard = (to, from, next) => {
+    if (from.name !== 'GroupNew' || this.hasContent()) {
+      return next()
+    }
+
+    if (
+      confirm(
+        '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+      )
+    ) {
+      removeDraftConfirmer()
+      this.cleanupContent()
+      return next()
+    }
+
+    return next(false)
+  }
+
+  mounted() {
+    this.$watch(
+      'group',
+      () => {
+        if (this.hasContent()) {
+          useDraftConfirmer()
+        } else {
+          removeDraftConfirmer()
+        }
+      },
+      { deep: true }
+    )
+    this.beforeEachControl = router.beforeEach(this.beforeLeaveGuard)
+  }
+
+  beforeDestroy() {
+    if (this.beforeEachControl) {
+      this.beforeEachControl()
+    }
+  }
+
   async submitGroup() {
     try {
       await api.groups.createGroup({ requestGroup: this.group })
@@ -67,6 +123,8 @@ export default class GroupNew extends Vue {
       alert('Failed to submit...')
       return
     }
+    removeDraftConfirmer()
+    this.cleanupContent()
     this.$router.push('/events/new')
   }
 }
diff --git a/src/workers/draftConfirmer.ts b/src/workers/draftConfirmer.ts
new file mode 100644
index 00000000..3e34ec84
--- /dev/null
+++ b/src/workers/draftConfirmer.ts
@@ -0,0 +1,13 @@
+const beforeUnloadListener = (event: BeforeUnloadEvent) => {
+  event.preventDefault()
+  event.returnValue =
+    '入力されたデータは送信されないまま破棄されますが，よろしいですか。'
+}
+
+export function useDraftConfirmer(): void {
+  window.addEventListener('beforeunload', beforeUnloadListener)
+}
+
+export function removeDraftConfirmer(): void {
+  window.removeEventListener('beforeunload', beforeUnloadListener)
+}