PURPOSE: To conduct safe control, and to facilitate carrying by inserting a key plate composed of the assembly of a plurality of two or more of plates to one cylinder lock under a combined state and releasing the lock.

CONSTITUTION: A tumbler 4 is fitted extending over the boundary of a rotor 2 and a cylinder 1, and a cylinder lock B is constituted so that the rotor and the cylinder are not moved mutually. The rotor 2 has a key plate A brought to a rotatable state to the cylinder 1 when the key plate is inserted to the cylinder lock B, and the key plate A is composed of the assembly of a plurality of two or more of plates 10a..., 10b.... Since the rotor 2 cannot be rotated to the cylinder 1 only by inserting each plate 10a..., 10b... to the cylinder lock B, the depth of key ways P1... is made to differ so as to be able to be turned freely only when the assembly of a plurality of the plates 10a..., 10b... are inserted to the cylinder lock B. When the assembly of a plurality of the plates 10a..., 10b... is inserted to the cylinder lock B, the engagement of the tumbler 4 projected to and retreated from the outer circumferential surface of the rotor and the engaging groove of the inner circumferential surface of the cylinder is separated completely, and the rotor 2 is revolved freely to the cylinder 1, thus releasing the lock.