To stop a closing operation of an opening/closing body by contact with an obstacle, and to improve safety of an automatic return operation of restarting the closing operation of the opening/closing body.

An automatic closing device 60 includes a pressurizing operation member 62 slidable in two directions and damper means 64, and is configured such that the pressurizing operation member 62 is slid in one direction to brake an operation part a3 by the pressurizing operation member in linkage with the movement in an opening direction of a movable seat plate 13 facing an opening/closing main body 11, and the pressurizing operation member 62 is slid in an opposite direction to release the operation part a3 by the pressurizing operation member in linkage with the movement in a closing direction of the movable seat plate 13 facing the opening/closing main body 11. The damper means 64 is configured to give almost no resistance to the sliding in one direction of the pressurizing operation member 62 but to give resistance to the sliding in the opposite direction of the pressurizing operation member 62 to reduce the moving speed in the opposite direction of the pressurizing operation member.