diff --git a/src/lib/markdown/internalLinkEmbedder.ts b/src/lib/markdown/internalLinkEmbedder.ts
index da2724194..210f75a75 100644
--- a/src/lib/markdown/internalLinkEmbedder.ts
+++ b/src/lib/markdown/internalLinkEmbedder.ts
@@ -2,7 +2,8 @@
  * https://github.com/traPtitech/traQ/blob/master/utils/message/replacer.goと同様
  */
 
-const mentionRegex = /:?[@＠]([^\s@＠]{0,31}[^\s@＠:])/g
+const mentionRegex =
+  /([@＠]([^\s@＠]{0,31}[^\s@＠:]))|(:[@＠]([^\s@＠]{0,31}[^\s@＠:]:))/g
 const userStartsRegex = /^[@＠]([a-zA-Z0-9_-]{1,32})/g
 const channelRegex = /[#＃]([a-zA-Z0-9_/-]+)/g
 
@@ -114,21 +115,28 @@ const replaceAll = (m: string, getters: Readonly<ReplaceGetters>) => {
 
 const replaceMention = (m: string, getters: Readonly<UserAndGroupGetters>) => {
   return m.replace(mentionRegex, s => {
-    // 始まりが:なものを除外
-    if (s.startsWith(':')) {
+    const isStartsWithColon = s.startsWith(':')
+
+    // 始まりと終わりが:なものを除外
+    if (isStartsWithColon && s.endsWith(':')) {
       return s
     }
+    const sColonRemoved = isStartsWithColon ? s.slice(1) : s.slice(0)
 
-    // .slice(1)は先頭の@を消すため
+    // .slice(1)は先頭の@および:@を消すため
     // 小文字化はgetter内で行う
-    const name = s.slice(1)
+    const name = sColonRemoved.slice(1)
     const uid = getters.getUser(name)?.id
     if (uid) {
-      return `!{"type":"user","raw":"${s}","id":"${uid}"}`
+      return `${
+        isStartsWithColon ? ':' : ''
+      }!{"type":"user","raw":"${sColonRemoved}","id":"${uid}"}`
     }
     const gid = getters.getGroup(name)?.id
     if (gid) {
-      return `!{"type":"group","raw":"${s}","id":"${gid}"}`
+      return `${
+        isStartsWithColon ? ':' : ''
+      }!{"type":"group","raw":"${sColonRemoved}","id":"${gid}"}`
     }
 
     return s.replace(userStartsRegex, s => {