To enable setting of a water level while making sanitary management in mounting work and maintenance appropriate by installing a pilot valve and a main valve outside a water tank.

A discharge regulator is composed mainly of the main valve 5, the pilot valve 6 and the water tank 9. Outside the water tank 9, there are provided the main valve 5, which is located in a valve body 4 equipped with an inlet 2 and an outlet 3 of water, so as to make the inlet 2 and the outlet 3 carry out opening and closing operations, and the pilot valve 6 which makes the main valve 5 carry out the opening and closing operations. A normal water level detecting pipe 7, which communicates with the pilot valve 6, and an adjusted water level detecting pipe 8 are provided inside the water tank 9, which is provided with an inflow port 10, communicating with the outlet 3, and an outflow port 11. The pilot valve 6 is constituted as a three-way valve. The water is made to flow into a cylinder 17 via a pilot valve body 21 by primary-side pilot piping 15, so as to close the main valve 5. The water is made to flow out from the cylinder 17 to a secondary side by secondary-side pilot piping 16, in order to open the main valve 5.