To provide a composite disk tumbler lock, capable of miniaturizing a cylinder lock.

This lock comprises an outer cylinder 1 having a cam groove 2 formed along a base line of the inner circumferential surface, an inner cylinder 3 rotatably fitted to the outer cylinder 1 and having a key hole 4 opened along the central axial line, and a locking bar 6 extended along the base line of the inner cylinder 3 and guided to be radially movable on the outer circumferential part of the inner cylinder, and having an outer edge to be engaged with the cam groove 2, which is energized in an outwardly protruding direction. A disk tumbler 9 having a key insert hole 11 capable of enclosing the key hole 4 is stored in each of a plurality of slots 8 and 8 provided along the central axial line of the inner cylinder 3 so as to be movable in the longitudinal direction, and an unlocking cutout 13 is formed on the side opposite to the locking bar 6 of the disk tumbler 9, so that when a spare key 5 is inserted to the key hole, the unlocking cutout of each disk tumbler is matched with the locking bar 6.