To dispense with maintenance work of a cylinder lock, while reducing a burden of securing and managing a storage place of a key of a contractor.

This lock device has a dead locking latch bolt 10 for putting an entrance door 1 in a locking state by being held in a state of being inserted into an opening part of the entrance door 1 and putting the entrance door 1 in a releasable state by being put in a movable state to the opening part of the entrance door 1, a solenoid 20 having an iron core 22 arranged in a position for making the dead locking latch bolt 10 immovable by fitting to the dead locking latch bolt 10 inserted into the opening part when an electric current is not carried and releasing a fitting state of the iron core 22 with the dead locking latch bolt 10 by current-carrying, an operation part 91 accepting input of user ID, and a control part 80 carrying an electric current to the solenoid 20 when succeeding in user authentication of the user ID by controlling the current-carrying to the solenoid 20.

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