To enhance security by improving convenience of use by a user without forcing a normal user to perform a cumbersome locking/unlocking operation, hardly causing an illegal intruder to perform the locking/unlocking operation, and increasing physical resistance against the fraudulent opening of an entrance door.

This lock device comprises: dead locking latch bolts 10 and 110 which are held in the state of being inserted into a hole portion, so as to put the entrance door into a locked state, and which are put into the state of being movable with respect to the hole portion, so as to put the entrance door into an unlockable state; a connecting member 20 for connecting the dead locking latch bolts 10 and 110 together; a lever handle which transmits a first operating physical force so as to move the dead locking latch bolt 10; and a connecting lever 60, a slider 40 and a locking lever 50, which put the entrance door into the unlocked state by moving the dead locking latch bolt 10 and moving the dead locking latch bolt 110 in synchronization with the movement of the dead locking latch bolt 10, in prescribed conditions.