The invention provides a locking device which comprises a foldable plate and a frame. A rotary lock buckle mechanism is arranged on the edge of the foldable plate. An elastic spring bolt mechanism is arranged at the lower end of a fixed plate perpendicular to the frame, and the rotary lock buckle mechanism comprises a rotary shaft seat and a rotary shaft arranged in the rotary shaft seat. A limiting mechanism is arranged at the upper end of the rotary shaft, and a self-locking nut is further arranged at the lower end of the rotary shaft. A lock head is fixed to a flat position milling rotary shaft through the self-locking nut. The elastic spring bolt mechanism comprises a lock seat and a lock opening preventing spring sheet arranged in the lock seat. A spring sheet of the lock opening preventing spring sheet stretches out of the lock seat to be matched with two calabash-shaped spring bolts, at the lower end of a rotary pin, on the lock head. The spring sheet is arranged between the two calabash-shaped spring bolts. The locking device is simple and compact in structure, high in reliability and reasonable in arrangement, the foldable plate can be opened and closed conveniently and fast, good locking performance is achieved, and noise can be lowered.