PURPOSE: To ensure safety at ordinary times while surely and rapidly release a lock from the outside of a room at the time of emergency by providing an operating lever integrated with a knob, a solenoid which is operable from the outside of a room and a rotary member supported by a dead bolt.

CONSTITUTION: A solenoid 27, an operating lever 36, a rotary member 15, etc., are provided on a lock device having a lock means consisting of a dead bolt 6 and, e.g., a cylinder lock 8. The solenoid 27 and the rotary member 15 are linked together via a cam member 28, a block 48, a trigger bolt 21, a pole 19, and a lever 18 so that the rotary member 15 is rotated to a retracted position where it is not brought into contact with, or a position where it is engaged with the operating lever 36 in accordance with the no-operating time or operating time of the solenoid 27. At the time of an emergency, when the bolt 6 is in a lock position, the member 15 is moved to the operating position and by rotating a knob, the lock can be released via the lever 36 by a specified person.