A drive of a steering-lock actuator is controlled such that a lock member takes a steering lock state from a steering unlock state if there occurs a change in the state of a vehicle door detected by a door-state detecting device and a stop state of the vehicle is detected by a vehicle-stop-state detecting device when an ignition switch is in an OFF state (step S7). A power supply to the vehicle-stop-state detecting device is made stop if the ignition switch is turned to the OFF state from an ON state (step S2), and the power supply to the vehicle-stop-state detecting device resumes if there occurs the change in the state of the vehicle door detected by the door-state detecting device when the ignition switch is in the OFF state (step S4).