A discharge valve apparatus has control cylinder members for controlling the flow of rinse water flowing out from a reservoir tank discharge port, on which opening portions are formed, and flow-adjusting members attached to these control cylinder members are capable of adjusting the opening surface area of opening portions in the control cylinder member. Female engaging portions in the control cylinder member are arrayed approximately vertically, and are furnished with registration indentations for registering the attachment positions of adjusting members relative to the control cylinder members. Intervals within the registration indentations are set to be smaller than a width of an installer's finger to prevent release of engagement by an installer when the adjusting member male engaging portions are in a state of engagement with the female engaging portions of the control cylinder members.