PURPOSE: To improve the facility of a valve in a valve device mainly applied to closet washing piping equipment by utilizing city water pressure for pilottical valve opening operation in an initial service condition.

CONSTITUTION: A valve body 26 is accommodated inside a valve casing 20 so as to be axially movable. The auxiliary valve seat 33 of the valve body 26 is provided oh the side of the fluid outlet passage 23 of the valve casing 20. An auxiliary valve body 35 corresponding to the auxiliary valve seat 33 is always energized to a closing direction by a spring 37. The valve casing 20 is provided with a valve seat 24, and the valve body 26 is provided with a working face corresponding to the valve seat 24. Since at the time of valve opening operation, pressure in the pressure chamber 31 of the valve body 26 pushes down the auxiliary valve body 35 and moreover acts in a direction where the auxiliary body 35 is separated from the auxiliary valve seat 33, force to push down a valve rod 34 can be satisfied with little strength because of the valve being opened.