A VoIP system has plural CPE units connected to an IP network as parties to be connected with each other. Each CPE unit is composed of a VoIP-IF circuit and an audio codec circuit. The VoIP-IF circuit executes at least one of the coding process to the first audio frequency signal and the restoration process to the media information to transmit the media information generated by the process to the party connected and restore the first audio frequency signal from the media information supplied from the party connected to output it. The audio codec circuit performs at least one of the sending of the received music data to the party and the conversion of the music data supplied from the party into the second audio frequency signal.