To provide an exhaust structure for an air valve, capable of restraining dispersion of splashing and preventing foreign particles from penetrating into the pressure chamber by restraining sudden pressure drop in a float chamber, when it is exhausted under pressure.

A large aperture 10 is formed above a valve case 1; and there are provided a valve body 18 inside the valve case 1, which opens or closes the large aperture 10; a float 22 via a shaft 20 below the valve body 18; and a pressure regulated board 26 on the lower side of the valve body 18, which is a large diameter than valve body 18 and which provides opposing flexibilities by peripheral edge 26b opening a predetermined gap around periphery of the large aperture 10.