To provide an opening and closing device which enables a lock device to operate smoothly.

This opening and closing device includes a lockable position detecting means 50 for detecting that an opening and closing body 10 falls within a positional range in which it can be locked by the lock device 40. When a value of a load detected by a load detection portion 37 reaches a preset opening load limit value during the opening motion of the opening and closing body 10 and when a detection signal transmitted by the lockable position detecting means 50 exists, the opening and closing body 10 makes a closing motion by a predetermined amount, so that a portion to be locked and a locking portion can be put into the state of being separated from each other in the opening and closing directions of the opening and closing body 10.