The present invention relates to an automatic door closer including: a main housing having the shape of a cylinder; a damper housing adapted to divide the interior of the main housing into an upper chamber and a lower chamber and having oil charged thereinto and a fixed vane formed at one side of the inner peripheral surface thereof in such a manner as to be projected toward the center thereof; a cover fixedly coupled to the upper periphery of the main housing; an activating shaft having one end extended to the outside through the cover in such a manner as to be rotatably supported and the other end rotatably supported against the bottom surface of the main housing through the damper housing; a rotary vane formed integrally to the outer periphery of the activating shaft so as to divide the interior of the damper housing into first and second chambers, together with the fixed vane; a return spring adapted to provide a returning force of returning the activating shaft to an initial setting position at the time when the door is closed; and damping means adapted to selectively provide a damping function if the activating shaft and the rotary vane are rotated in a closing direction of the door.