A speaker includes a protector (67) which protects a speaker main body, a speaker opening (54) formed in one side surface of the speaker main body, a speaker sound hole (55) formed in the protector, and a cushion member (52) arranged on the protector. The speaker is attached to a rear side case (21) such that the speaker opening opposes a housing sound hole (21a) formed in the side surface of the rear side case (21) of a mobile telephone. Hence, a cavity (50) communicating with the housing sound hole is formed between the protector of the speaker and the major surface of the rear side case. With this structure, a distance from the speaker opening which outputs a sound generated by the speaker main body to the housing sound hole becomes shorter than in the conventional case, and the cavity can be utilized as an acoustic transfer space. Even when the mobile telephone is made thin, an increase in acoustic resistance can be suppressed, and deterioration in characteristics of a speaker output sound can be decreased.