To reduce the chances of a vehicle suffering theft.

First and second control units 1 and 11 are connected by a two way communication means 12. The vehicular anti-theft device is provided with a means 1 of verifying an identification code stored in the control units 1 and 11 via the communication means 12 when a change-over from an off position to an on position of an ignition switch is detected, a timer means 1 of measuring elapsed time from a predetermined measuring start time, a means 1 of determining whether or not the identification code has been verified after the change-over of the ignition switch, and a means 1 of obstructing starting of a vehicle when the verified identification code does not match a predetermined combination or the identification code is not verified and the elapsed time has exceeded a set time.