To provide the portable acoustic device that informs the user directly of the arrival of an incoming call in voice to a portable telephone set through a headphone or the like in use even when the portable acoustic device is in use.

The portable acoustic device 14 receives an incoming call notice signal 16 sent from a portable telephone set by an incoming call recognition 15 and uses a demodulation circuit 17 to demodulate a received incoming notice signal. A sound signal 18 such as a music software or the like from a sound source is outputted to a headphone or the like of an external connection device 21 from an external output section 20 via a signal synthesis circuit 19. When the incoming notice signal 16 is sent from the portable telephone set to the headphone 21 when the acoustic device is in use, the incoming call notice signal demodulated via an incoming call reception circuit 15 and the demodulation circuit 17 is given to the signal synthesis circuit 19, where the signal 16 is synthesized with a voice signal 18 and the synthesized signal is outputted to the headphone 21 so as to inform the user of the arrival of an incoming call in voice or the like.