To provide a cylinder lock set that controls the key insertion position for releasing the lock without providing any protrusion useful in picking or the like on the rotor side.

The cylinder lock set comprises a lock release key 2 of which the shaft part 1 advances and retreats within a key insertion hole 3 where the key 2 can be inserted in both its regular insertion position and the reversed position, and a cylinder lock 7 in which a rotor 5 having plural tumblers 4 each with a scoop 11 at its end near the key insertion hole 3 is rotatably inserted into a cylinder case 6. An insertion guide protrusion 8 is provided at the tip of the lock release key 2 in a deflected position relative to the longitudinal center line of the key insertion shaft 1. At least one of the tumblers 4 is arranged so that its scoop 11 can be positioned below the line along which the insertion guide protrusion 8 of the lock release key 2 is inserted, and this prohibits the lock release key 2 from being inserted in the reversed position.