PURPOSE: To increase the water depth permitting overflow over the wider range by reducing minimum height of a gate by providing a falling gate in a tilting manner on the upper part of the uppermost stage water gate of a multi-stage type gate consisting of two or more stage water gates.

CONSTITUTION: A lower stage gate 1 and an upper stage gate 2 having a height H2 is provided to a support structure having a maximum gate height H1 in a vertically movable manner. A falling gate 3 of the same width as the upper stage gate 2 is provided in a tilting manner to the upper part of the upper stage gate 2. If h/h + H2 = K(where h is the adjustable allowance of the falling gate 3), H2/H1 =1- K/2 - K is obtained, and therefore, when the value of (h) is increased to increase the value of K, the H2/H1 ratio can be made smaller than that in the conventional type. In case where water depth is 2H2 or more and the amount of overflow is small, the falling gate 3 is tilted and the height (h) is adjusted to regulate the amount of overflow. In case where the amount of overflow is much or water depth is 2H2 or less, also, the upper stage gate 2 is lowered and the amount of overflow is finely adjusted by tilting the falling gate 3.