A portable electronic device includes a casing, a key, a loudspeaker, a soft insulating material, and an actuating unit. The key is disposed at the casing. The loudspeaker is embedded into the casing flatly. The soft insulating material covers the casing and the loudspeaker. The actuating unit is coupled to the key and the loudspeaker, and it actuates the loudspeaker to protrude from the casing in response to an actuation of the key.