A main control ECU of a vehicle unit performs mutual communication with a portable device by external transmitters when respective vehicle doors provided with the automatic open/close function are open. The main control ECU further performs, after ID code matching is confirmed, the mutual communication with the portable device by the external transmitters again after a predetermined time. The main control unit still further performs, when the second matching is not confirmed, mutual communication with the portable device by an internal transmitter. The main control unit automatically closes the vehicle doors when the third matching is not confirmed.