PURPOSE: To make improvements in an antitheft effect in making constitution simpler and structure stronger by installing a turning angle detecting mechanism in a gear rotating in linkage with a rack installed in a card, and when a turning angle of the gear has accorded with the setting value, having a lock released.

CONSTITUTION: In a metal card 1, there are provided with plural pieces of racks 2 which has the number of teeth regulating each unlocking and forms a gear into a vertical form. Also there is provided with a gear 4, corresponding to the racks 2, fitted with a grooved pulley 6 with a notch 5 or a detecting part at the lock side, and a grooved pulley receiving tongue part 9, forming a turning angle detecting mechanism, is installed as well. When the card 1 is inserted and the gear 4 and the grooved pulley 6 are rotated each as many as the number of teeth, the notch 5 is aligned in a straight line, and further this notch 5 gets into the tongue part 9 by thrust force of the card 1, and an unlocking linkage lever 12 is rotated via a shaft 10 and a hole 11, thus a lock is released.