To provide a hydraulic machinery having small idling input during idling operation such as the phase modifying operation on the pumping waiting operation, with little fluctuation.

The hydraulic machinery of this invention is provided with a runner, a casing connected to an outside of a runner chamber, a guide vane interposed between the runner and the casing, a draft tube connected to a lower part of the runner chamber, and a drain system for connecting the runner chamber and the draft tube to each other so as to drain the water inside of the runner chamber. A drain port opened in the runner chamber is structured so that a circumferential length position of a cut piece around the rotary axis of the runner is formed equal to or more than the diameter of the inner wall of the runner chamber opposite to the maximum diameter of the runner. With this structure, the idling input during the idling operation such as the phase modifying operation on the pumping waiting operation can be restricted small, and the fluctuation is restricted small.