To provide an opening/closing valve having an opening display function with an opened condition easily visible.

When a valve stem 15 of an opening/closing valve 1 is rotated in a fixed direction by a handle 26, a valve element 10 is separated from a valve seat 7, to open a passage hole 3. Here in this constitution, an annular groove 19 in a display part provided in the valve stem 15 is exposed outside from a nut unit 22 so that an opened condition of the opening/closing valve is made visible.