To provide a crescent lock which prevents illegal releasing of a crescent lock even when a glass plate of a window is broken and fingers or a tool is inserted from the outdoor, improves the locking reliability, and facilitates locking, fitting and replacement thereof.

By providing fitting parts engaged with a crescent body and a handle, respectively, the handle is made to be attachable to and detachable from the crescent body. By housing a rotation regulating mechanism, which includes an engaging groove of a rotary shaft, an engaging plate, a shaft body, a tension coil spring and a base except the fitting part of the rotary shaft and an engaging body integrated with the rotary shaft, in a housing space of the crescent body, the engaging plate is fitted into the engaging groove of the rotary shaft by the interposition of the tension coil spring when the handle is pulled out of the crescent body in a locked state, and the rotation of the rotary shaft is regulated. Namely, the rotation of the engaging body is also regulated and a state of locking is obtained. The locked state can be released only by reinserting the same handle into the fitting part of the crescent body.