An automatic door closing hinge is configured in such a manner that first balls (43) are engaged with a first cam groove (35) formed on an outer peripheral surface of an operating rod in a cylinder (2) at opposed positions so as to have a substantially V-shape at opposed positions thereof, the first balls (43) are engaged with a compression ring (4) urged downward by a compression coil spring (5), the movement of the first balls (43) with respect to the first cam groove (35) is in conjunction with the movement of the compression ring, second balls (65) are engaged with a second cam groove (36) formed under the first cam groove (35) and having substantially the same shape as the first cam groove (35), the second balls (65) are engaged with the piston (6), the movement of the second balls (65) with respect to the second cam groove (36) is in conjunction with the movement of the piston, and air on the lower side of the piston (6) in the cylinder is gradually flowed out according to the movement of the piston.