An audio apparatus for a vehicle made up of a car-mounted audio apparatus 100 and portable audio apparatuses 200a and 200b transmits/receives contents data such as music via radio communication. As a communication system for this in-car radio communication, a short-distance data communication system is used, which allows the apparatuses to recognize and authenticate one another and perform data communication with one another in the vehicle. Received music data is reproduced/output in real time.