An audio jack for receiving an audio plug includes a connection hole with a position detection portion and a first audio channel contact portion therein. When the audio plug is inserted into the connection hole to the linking position, a first audio channel connection portion of the audio plug contacts the position detection portion and the first audio channel contact portion. The position detection portion and the first audio channel contact portion respectively have a first distance and a second distance to an opening of the connection hole, wherein the second distance is smaller than the first distance.