To provide a simple structure capable of using a general card by retreating a pin stopper at the tip to make the engagement pin of a cylinder lock rotatable.

A guide piece fitted to the fitting recessed part of the rear frame 2c of a base plate 2 is removed. According to this, since the rear edge of a card key 16", when inserted to the recessed part of the base plate 2 on the bottom plate of a casing, makes contact with the inside of the frame 2c, a locking plate 5 retreats to the lockable state of a cylinder lock. Thus, since the engagement pin 9 of a latch presses down and retains a working plate in the state where the cylinder lock is locked, and its card key stopper projects into a card key insert port through the hole of the base plate 2, both the taking out of the internal card key 16 or the new insertion are prevented. Accordingly, a general card key can be easily used, and the structures of both the card key and the lock device can be simplified.