To provide a smart keyless device of a vehicle which can provide an immobilizer function thereto without separately setting a radio-signal generation means or an aerial used for sending a radio signal.

Either the predetermined radio-signal generation means or the aerial used for sending a radio signal used for the smart keyless authentication communication (s2, s3) is shared with the radio-signal generation means or an aerial used for transmitting and receiving a radio signal used for the immobilizer authentication communication (s5, s6). Then the smart keyless control means is provided with the receiving means for the immobilizer authentication communication and a startup control means. The receiving means for the immobilizer authentication communication performs receiving control of a radio signal from the transponder received by the aerial used for transmitting and receiving the radio signal used for the immobilizer authentication communication which is shared (s6). The startup control means performs startup control of an engine (s8) based on the received signal from the receiving means used for the immobilizer authentication communication.