To provide a hook lock with which an existing door lock can be easily replaced, and in which an anti-abnormal-operation mechanism of a dead bolt for use in the prevention of the overcurrent of an electric drive motor is built.

A slider unit 101 is fitted into the outer peripheral part of a dead bolt unit 6, and urged to a normal position by a dead spring 10 which is provided in the dead bolt unit 6. A hook unit 7 is arranged in the dead bolt unit 6, and operated by using a hook operating shaft 13. When the slider unit 101 is slid in a locking direction by a potbellied gear unit 17 in locking, the dead bolt unit 6 is also slid in the same direction via the dead spring 10. When the dead bolt unit 6 cannot be operated due to some sort of an abnormal state, only the slider unit 101 is moved, and the dead spring 10 is charged. When the abnormal state is eliminated, the dead bolt unit 6 is shifted to the locking position by the dead spring 10.