To provide disc tumbler type cylinder lock with high crime preventive performance which is never easily illicitly unlocked.

This cylinder lock comprises an outer cylinder 5 having engagement grooves 3 and 4 on an inside surface 2; an inner cylinder 8 having an axial hole 6 and a radial through-hole 1 in the inner part; and a disc tumbler 9 energized by the elastic force of a spring 10 and engageable with the engagement grooves 3 and 4 of the outer cylinder 5. The engagement groove 3 for engaging the upper end of the disc tumbler 9 has a clearance larger than the engagement groove 4 for engaging the lower end with the upper end of the disc tumbler 9. Even if the lower end of the disc tumbler 9 is engaged with the engagement groove 4 to rotate the disc tumbler 9 to the right with the inner cylinder 8, the upper end right angle of the disc tumbler 9 does not get on the boundary angle part between the inside surface 2 of the outer cylinder 8 and the engagement groove 3, and the upper end part of the disc tumbler 9 is engaged with the engagement groove 3 by the energizing force of the spring 10. Accordingly, this disc tumbler type cylinder lock 1 is never illicitly unlocked.