To provide a locking and unlocking mechanism, which makes a panel surface have a smooth appearance when a door is closed, enables the door panel to be easily locked and unlocked from outside, has no projections on the circumference of an opening when the door is opened, has excellent appearance, and stands clear during access time to work to the opening.

A locking and unlocking mechanism 1 comprises a door panel 2, a receiving member 3, and a lock device 4 which locks and unlocks the door panel and the receiving member to each other. The door panel 2 has a flange part 8, and is hung on one of neighboring studs C with a hinge. The receiving part 3 having the lock device 4 therein is fixed to the other stud C, and comes in contact with a flange part 8 of the door panel 2 to constitute a continuous wall body W having a smooth surface when the door is closed. A joint part W4 between an edge 8a of the flange and a counter edge 11 of the receiving member 3 is provided with a key insertion hole 12a. A key 18 is inserted from the hole to rotate a latch plate 16 for locking or unlocking operation. The latch plate 16 is retractable from an edge plate part 13 of the receiving member 3 to engage or disengage a free edge 7 of the door panel 2.