PURPOSE: To ensure the safety of control of a gate in an emergency, to constantly keep the gate on standby, and to reduce the cost of the gate.

CONSTITUTION: An automated emergency door shutting device has a reclining dam 7 provided in such a manner as to freely rotate with one end supported to an axis, a cylinder 8c provided diagonally behind the axially-supported portion of the reclining dam 7 in such a manner as to freely rotate with one end supported to an axis, an arm 8g for connecting the piston rod 8d of the cylinder 8c to the reclining dam 7, and a suction and exhaust system 10 for actuating a piston 8d inside the cylinder 8c, the place of installation of the cylinder 8c being separated from that of the suction and exhaust system 10 by lines 10h, 10g. When air is fed into the cylinder 8c the piston rod 8e expands and the reclining dam 7 is erected; when air is vented the reclining dam 7 is turned down. Also, remote control is simplified by extension of the lines 10h, 10g.