To solve a problem that a duplicate key is created to unlock in some cases when identification code information inside a key and a lock is stolen in a vehicle antitheft system provided with an electronic locking device.

When a vehicle key 7 is inserted in an electronic cylinder lock 2 of a vehicle, the ID of the vehicle key 7 is read by a vehicle key ID acquisition part 5, and a vehicle ID is read from an ID storage part 9 by a vehicle ID acquisition part 8 of an in-vehicle device 1. A device control part 14 transmits the acquired vehicle key ID and the vehicle ID by a sender's number notifying function to a center device 21 through a cellphone 17 connected to an external equipment interface 13. The center device 21 collates the received vehicle key ID and the vehicle ID with the cellphone number in an ID collating part 23, and when in agreement, sends a response of authentication acceptance to the in-vehicle device 1 through the cellphone 17. The in-vehicle device 1 unlocks the electronic cylinder 2 when the authentication response is acceptable.