To prevent regular initial fastening force from not being given by deformation-damage of a lock device for a hanging clamp by external force.

The lock device 30 for the hanging clamp 10 is provided with a latch 34 turnably connected to a clamp body 11; and a lock spring 31 connected to the latch and acted so as to urge the cam to a direction projected to an opening 14 by transmitting the tension to the cam 18. It can be switched/operated to the lock operation state that the camp is projected to the opening by applying the tension of the lock spring and the initial fastening force is given to a workpiece inserted to the opening and the lock non-operation state that the tension of the lock spring is not applied to the cam. Since a latch stopper pin 41 is provided on the latch, the latch is retained at the same position even when the latch in the lock non-operation state receives the external force, and deformation-damage of the lock spring is prevented.