To prevent the theft of a vehicle or internal articles by measuring an elapsed time from receiving when unlocking signals for a vehicle door with remote operation is received and cancelling a warning mode when operating as predetermined in a preset time.

A warning mode to be applicable or not is identified by a step S11 and, if not, the step returns to an original and, if applicable, a counting timer to start from unlocking operation for S12 remote operation is identified. If a timer has been started, a S13 preset time to elapse or not is identified and, if not, a door to be unlocked or not with S14 remote operation is identified and, if unlocked, the timer starts and it returns to S11 and, if not unlocked, the S16 door to be open or not is identified and, if left closed, it returns to S11 and, if open, an alarm such as a S17 horn is issued and it returns to S11. If a S13 preset time elapses, it returns to S19 and, if not, it returns to S18 and, if the door is open, a S20 engine to be rotated or not is checked and, if rotated, it changes into a S21 not-warning mode, a S22 timer stops and it returns to S11 and, if closed, it returns from S18 to S11. In a step S19, if the door is open, the alarm is issued and it returns to S11 and, if closed, it returns to S11. If careless unlocking occurs with locking misoperation, effect on theft can be held.