A discharge valve apparatus of the present invention includes: a discharge portion main body member attached to discharge opening, forming the inside of discharge flow path for guiding flush water from an inflow opening formed at one end thereof to an outflow opening formed at the other end thereof; a valve body for opening and closing the inflow opening of the discharge portion main body member; and an affixing portion, formed to project into the discharge flow path of a discharge portion main body member, for affixing the discharge portion main body member to a reservoir tank; wherein the inside surface of side wall portion in the discharge portion main body member at the same height as this affixing portion forms a curved portion, which curves outward so as to expand the cross-sectional area of the flow path.