To provide a butterfly valve having an anti-cavitation function, that prevents the occurrence of erosion and capable of finely adjusting a volumetric flow rate of fluid in an area of low degree of valve opening or in an area of minute degree of valve opening to infallibly attain high range ability and excellent control and tight shut functions.

The butterfly valve is for opening and shutting an interior of an elastic seat ring 2 mounted in a cylindrical valve casing 1 by rotation of a disc valve member 3, wherein an outer peripheral edge of the valve member 3 on an orifice side 8 of the valve member 3 is directed toward a downstream side, and an outer peripheral edge of the valve member 3 on a nozzle side 9 is directed toward the upstream side, and a wing-like depressing valve parts 10, 11 having a spherical outer periphery is provided to each of the orifice side 8 and the nozzle side 9. The depressing valve parts 10, 11 are adapted to make depressing contact with the elastic seat ring 2 in the area of minute degree of opening of the valve member 3, and an orifice side valve stopping part 3a is formed in a state inclined toward a valve primary side with respect to a nozzle side valve stopping part 3b.