Abstract: A flush valve for a toilet, the flush valve including a main valve unit for causing a main valve body to reciprocate between a closed position and an open position in response to pressure inside a back pressure chamber communicating with a primary side flow path thereby opening and closing a flow path between the primary side flow path and the secondary side flow path. The flush valve further including a sub-valve unit having a sub-valve body for opening and closing a bypass flow path connecting the back pressure chamber and the secondary side flow path. The flush valve further including a generating unit disposed on the downstream side of the main valve unit and serving as flow path resistance on the secondary side flow path. Wherein the bypass flow path is connected to the secondary side flow path downstream of the generating unit.

Abstract: [Problem] To provide a flush valve capable of providing flush water at a high force. [Means for solving the problem] A flush valve 1 connected on the downstream side to a toilet 2, comprising: a main valve unit 10 for causing a main valve body 11 to reciprocate between a closed position and an open position in response to pressure inside a back pressure chamber 27 communicating with a primary side flow path A, thereby opening and closing a flow path between the primary side flow path A and the secondary side flow path B; a sub-valve unit 30 having a sub-valve body 31 for opening and closing a bypass flow path 25 connecting the back pressure chamber 27 and the secondary side flow path B; and a generating unit 50, disposed on the downstream side of the main valve unit 10 and serving as a flow path resistance on the secondary side flow path B; wherein the bypass flow path 25 is connected to the secondary side flow path B downstream of the generating unit 50.