To provide an inexpensive downsized opening/closing device of a hinged door, which has a door closing buffer mechanism and a door opening fixing mechanism enabling a door to be temporarily fixed midway through a door opening operation according to need, and which is provided with the door closing buffer mechanism, the door opening fixing mechanism, etc. in such a manner that a hinge serves as a main member.

This door opening/closing device 1 comprises the door 2, a door frame 3 and the hinge 4. The hinge 4, which is rotatably and pivotally mounted on the base end 2a of the door 2 and the base end 3a of the door frame 3, is composed of a shaft 42 of the hinge 4, and hinges 43a and 43b which are externally mounted on the shaft 42 so as to be opened/closed rightward and leftward. The hinge 4 and the door frame 3 are each provided with the door closing buffer mechanism; the door closing buffer mechanism is composed of a coiled spring 41 which urges the door 2, mounted on the hinge 4, in a closing direction, and a small-sized absorber 5 which is attached to the door frame 3. The hinge 4 is provided with the door opening fixing mechanism. The door opening fixing mechanism is locked by fitting a resilient protruding tongue piece 46, provided on the frame side of the hinge 4 and protruded in a door opening direction on the shaft side, into either of a recess 47 and a vertical recessed groove 48, provided in the door opening direction on the rotating shaft side of the hinge 4.