To reduce the number of parts to the utmost.

In a temporary locking/unlocking device of a lock, a temporary locking piece is assembled by a fixed shaft in a lock case so as to engage with an engaging counterpart of a protruded engaging member retractably set in the lock case. Meanwhile, a pushing actuation piece having a receive plate selectively receiving inside/outside pushing pieces projecting inside from an aperture of the lock case and a pushing plate pressing the sliding part of the temporary locking piece respectively is arranged at the back side of the temporary locking piece. Further, the middle part of a return spring is wound up on the fixed shaft, one end thereof is brought into contact with the edge of the front opening of the temporary locking piece and the other end is allowed to pass through the rear opening of the temporary locking piece and brought into pressure contact with the spring holder of the pushing actuation piece. When closing the door, as the pushing piece lifted up, the pushing actuation piece vertically moving, resulting from the movement of the pushing piece cooperates with the temporary locking piece moving around the fixed shaft as a fulcrum so that the fixing part of the temporary locking piece is engaged/disengaged to/from the engaging counterpart of the protruded engaging member.