PURPOSE: To make the same card as a credit card usable as well as to promote low-unit cost of production by moving a slide body with a spring energizd, operating a lock pin and performing a job for unlocking and vice versa.

CONSTITUTION: A slide body 13 sliding by means of spring energization is installed in space between a lock body and a fixed body 12. Next, there is provided a lock pin 16 which locks the slide body 13 in respective fitting hole 12a, 13a at both sides of the fixed body 12 and the slide body 13. In succession, a card key insertional hole 18 is installed in the slide body 13, on a surface of a card key 20, an uneven pattern 21 is formed in a corresponding position of the lock pin 16. Subsequently when the key is inserted thereinto, the stepped pin 16 pushes the surface upward with the projection 21, eliminating the step difference, thus unlocking takes place. In addition, the slide body 13 is shifted by operation of the key 20, so even at a recess 21a, unlocking can be done too. Then, the key is pulled out of the inserional hole 18 and the slide body 13 is reset by a reset spring 14, thus the slide body 13 is made into a state of being locked.