PURPOSE: To prevent illicit use or the like positively by setting two identification codes in an IC-built-in key as a card key, and rewriting the identification code and also the door gate side identification code on the door gate side.

CONSTITUTION: When a guest inserts an IC card into a card reader 9 at the time of entering a room, a controller 7 on the door gate side collates a room number and the like. In the case of the collation being discordant, the NG lamp of the card reader 9 is lighted to refuse lock release. In the case of coincidence, a key identification code and a door gate identification code are further collated. In the case of the card 1 being a legally issued unused card, the key identification code is rewritten into a memory 13, and the door gate identification code is rewritten at the same time. After confirming the pull-out of the card 1, an OK lamp provided at the card reader 9 is lighted to release the lock and to lock again after the guest entering the room. At the time of check- out, the guest returns the IC card 1 to the front, and the key identification code of the returned card 1 in the memory 13 is effaced at the front.