To provide a flush valve device capable of smoothly carrying out the actuation of the main control valve of the horizontally sliding flush valve device.

The flush valve provided with the main control valve, of which the center line is horizontal and rotatable around the center line, controls supply of flushing water. The main control valve is interposed between a main valve chamber connected to communicate with the inlet and the outlet and controls the flow of flushing water with a pressure chamber installed at the other side of the main control valve. Blades are formed radially at an equal pitch and a guide in which the distance of mutually adjacent blades is set to be 90° at most around the center line of the main control valve is provided.