To provide a lock breakage preventing device enhancing safety as a lock, achieving reliable operation and reduction in cost.

A handle lock 1 is provided with an operating device constituted by mounting a guide member 23 which is a bar-like body of a circular cross section, coaxially to a rotating output shaft of a motor 22, winding a sparsely wound spiral coil spring 24 around the guide member 23 movably in the length direction of the guide member, providing the center in the length direction of the outer peripheral surface of the guide member protrusively with a single protrusion 25 freely movable in a pitch clearance of the spring, and extending both ends of the sparsely wound coil spring outward. The extended portions of the spring of the operating device are engaged with a lock piece 26 provided substantially in parallel with the guide member so as to be detachably engaged with a handle cylinder.