PURPOSE: To intake and discharge small and large volumes of air and to intake or discharge a large volume of air so as to shorten the time of supply and discharge of water during filling or discharging water into and from a fluid pipe.

CONSTITUTION: A valve element 11 in a valve chamber 5 is divided into a lower valve 17 coupled to a float 9 and an upper valve 17 adapted to be seated on a large diameter vent hole 13a during upward movement, Both valves 16, 17 may be moved up and down, independent from each other, a small diameter vent hole 28 which is formed, vertically piercing through, in the upper valve 17, is closed when the lower valve 16 is seated.