PURPOSE: To further enhance safety, and easily perform installing work without generating a clearance between both by locking a door without looseness even if an error exists in an engaging condition of a receiving lever and a locking unlocking part.

CONSTITUTION: A key device is provided with a locking unlocking operation part 40, a locking unlocking part 5 to be locked and unlocked by operation of the locking unlocking operation part 40 and a receiving lever 2 to be put in a locking condition when the locking unlocking part 5 is locked, and the locking unlocking part 5 is provided with a bill-shaped projecting piece 50 and a rotary member 42 to rotate the bill-shaped projecting piece 50. The bill- shaped projecting piece 50 can engage with the receiving lever 2, and a receiving lever pressing-down member 8 having an oblique line 30 which can come into contact with the engaged receiving lever 2 is arranged on the engaging part side so as to be freely protrusible.