The invention relates to a locking device comprising a lock bottom plate. A left slideway, a lock cover plate, a brake wire seat, a right slideway, bolt sleeve seats, a lock slide rail pad and a guide rail in a guide rail slider pair are mounted on the lock bottom plate fixedly. Rack lock catches are arranged on the inner sides of both the left slideway and the right slideway. The lock cover plate, the brake wire seat and the guide rail slider pair are arranged in the middle of the upper end of the lock bottom plate, a lock slideway seat is fixedly mounted on the upper surface of a slider of the guide rail slider pair, a brake wire is connected between the brake wire seat and the lock slideway seat, and two symmetrical lock slideway parts are fixedly mounted on the upper surface of the lock slideway seat. A bolt sleeve is arranged between the two bolt sleeve seats, two bolts capable of sliding relatively is arranged in the bolt sleeve, a bolt compression spring is arranged between the two bolts, multiple racks are arranged at the outer end of each bolt, and multiple tooth sockets are formed in the inner end of each rack lock catch. The locking device locks relative moving parts when the moving parts move to different relative positions, and is simple, compact, safe and reliable in structure.