PURPOSE: To simplify a mechanism and operation, by a method wherein, in the subject device in which a cylinder gate is caused to expand and contract resulting from the increase and decrease in air and water in a tank, flat star-shaped tanks are mounted on the periphery of each cylinder, and air can be pressed into the tanks and exhausted therefrom by means of a control valve.

CONSTITUTION: A top cylinder 5, a medium cylinder 4, and a bottom cylinder 3 are flexibly connected together in a sliding manner. Flat star-shaped tank groups 31, 32, and 33 are mounted on a periphery of each cylinder, and the top cylinder 5 is caused to move vertically through pressing-in or suction of air into a lifting tank 32 on the top cylinder 5 through the working of an air compressor 16, located on an upper top plate of a cylinder gate, a pipe line 27, a control valve 12, and a feed and exhaust hose 23. Air is pressed into a lifting tank 31 on the bottom cylinder 3 through an air feed pipe 29 embedded in a ground 1, and this permits the vertical movement of the cylinder 3 to expand and contract each cylinder.