PURPOSE: To suppress an automatically locking function by simple operation, by additionally providing an automatic locking-suppressing function in a lock device imparting the automatic locking function in a dead bolt.

CONSTITUTION: When automatic locking is performed, a trigger bolt 4 is sunk in a case 1 when a door is closed, engagement with a slider 10 is released by tilting a stopper 9. Next, the slider 10 is moved, a cam plate 18 is turned, a dead bolt 25 is protruded from the case 1, and a lever 33 of a guard lever 32 is engaged with a stepped part 30 of the bolt 25. When an automatic locking function is suppressed, a tip end of the dead bolt 25 is retained by a finger to be prevented from protruding, also the trigger bolt 4 is pressed in by a finger to a retraction amount or more when the door is closed. The bolt 4 is locked by fitting a protrusion part 9a of the stopper 9 to a lock groove 4b of the trigger bolt 4.