The invention discloses a locking device. The locking device comprises a sleeve tube and an inner tube arranged in the sleeve tube, wherein a locking element capable of being locked with the sleeve tube at opposite positions is arranged in the inner tube; the locking element comprises a locking support arranged in the inner tube; a locking block capable of transversally sliding relative to the locking support is arranged on the locking support; an inner tube through hole and a sleeve tube through hole are formed in the tube walls of the inner tube and the sleeve tube respectively; a locking pin capable of sliding in the inner tube through hole and the sleeve tube through hole with the locking block during the transversal slide of the locking block are arranged on the locking block; an inclined strip-shaped hole is further formed in the locking block; a drive device capable of sliding in the inclined strip-shaped hole thus pushing the locking block to transversally slide is arranged in the inner tube. The locking device disclosed by the invention is simple in structure, convenient to operate, reliable in running, and capable of driving the sleeve tube and the inner tube to unlock or lock from the interior of the sleeve tube.