To provide a locking device making it difficult for a detachable handle for locking, to be inserted into a handle insert passage.

A locking device is formed so that a first rotating member 3 is rotated to engage or disengage a claw fitting 10 from a fixed frame when a handle is inserted and rotated. A covering member 4 is fixed to a front end part 3a of the first rotating member 3 so as to form a space covering the front end part 3a and extending circumferentially between the covering member and the front end. A second insert port 4a leading to a first insert port 3c in which the handle of the rotating member is inserted is formed in the covering member 4. Then, a blocking member 6 capable of blocking the insertion of the handle is installed between the first insert port 3c and the second insert port 4a, and the blocking member 6 is released by the second rotating member 5 capable of being rotated by a key, thus enabling the handle to be inserted.