To provide a disc tumbler lock having improved security which is strong against criminal unlocking by picking means such as wire or the like.

A rotor 2 is housed in non-movable manner in a shaft direction in a fixed external cylinder 1, a tumbler storing hole 4 is provided in a diameter direction of the rotor so as to cross the keyway in the axial direction of the rotor, a tumbler disengageable groove 6 is provided on the inner peripheral surface of the fixed external cylinder, a disc tumbler 5 stored in a movable manner to the tumbler storing hole is moved and energized by a spring 7 so as to link the tip portion to the tumbler disengageable groove, the key code portion unevenly formed at the side portion of the key comes into contact with the edge surface 10a of key inserting hole 10 of the disc tumbler, in a disc-tumbler lock made the tip portion of the disc tumbler disengageable from the tumbler disengageable groove, a disturbing recessed portion 11 having a shape and a dimension not permitting the entry of a key code portion 9 is formed on the edge surface of the key inserting hole of the disc tumbler with which the key code portion of the key comes into contact.