To change motion of fluid with a pressure into circular motion, and change every motion where a biased fluid motor acts on into the circular motion.

A rotary gate valve is decentered and is housed in a gate frame 2. A rotor is decentered and is housed in a rotor frame 12. The biased fluid motor has a shape where one side of both ends of the gate frame is a suction port and other side is a discharge port in a shape formed when the rotary gate valve and the rotor rotate at constant angles in a same direction and abut on each other. The respective rotors of the respective biased fluid motors are connected by rotation shafts while a direction angle of the rotor is changed so that the rotor of one fluid motor does not block the suction port when the rotor of the biased fluid motor blocks the suction port.