PURPOSE: To cut down the costs of facilities and maintenance by a method in which a crane is provided to a float movable on water, a runway deck is supported by the crane in a vertically movable and variably inclinable manner, and an apron plate is attached through a rotary shaft to the runway deck.

CONSTITUTION: A crane 5 is provided on a float 2, a wire rope 4 is wound up by winches 6a, 6b, 6c, and 6d to support a runway deck 3 at support points 3a, 3b, 3c, and 3d. Apron plates 7a and 7b are provided through rotary shafts 8a and 8b to both ends of the runway deck 3. When the winches 6b and 6d on the departure and arrival side of barges are wound up concurrently, only the barge side of the deck 3 is raised to change the inclination. Also, when it is moved, the deck 3 is raised by the crane 5 to support it midway of the strut 12, the wire rope 4 is removed, and the rotary table 11 is turned to direct the deck 3 toward the longitudinal direction of the float 2.