PROBLEM TO BE SOLVED: To arbitrarily set a water level at which a door body starts to rise.SOLUTION: A floating flap gate 1 is configured to raise and move a tip of a door body 2 around a rotation axis 2c located at a base end in a direction of water flowing in, and in a plane in a height direction, in order to close an opening of a tide barrier or a breakwater when the water flows in. A counterweight 7 is fixed at the other end of a wire rope 4 having one end fixed to a tip 2b of the door body 2. A stopper 8 is fixed to the wire rope 4 located between the door body 2 and a pulley 6a for guiding first the wire rope 4 fixed to the tip 2b of the door body 2. The wire rope 4 located between the stopper 8 and the door body 2 passes through a hollow first buoyance body 9 so as to be relatively displaced with respect to the wire rope 4. The door body is kept horizontal for a vehicle or the like to travel or evacuate at a water level where the vehicle or the like can travel.
