To solve a problem that efficiency is reduced when converting hydraulic power energy into electric power because a rotary shaft, a bearing supporting the rotary shaft, and a bracket supporting the bearing become resistance components for a water stream in a hydraulic power generator having a system for arranging an impeller having the rotary shaft in a cylindrical frame and fixing a rotor to a tip of the impeller.

The power generator rotor is fixed to the tip of the impeller which is not provided with the rotary shaft arranged in a cylindrical casing, and the rotor is rotatably stored and positioned in the casing to rotate the impeller by a water stream in the casing. The power generator rotor rotates in the same way as the rotation of the impeller to take electric power out of winding of a power generator stator arranged in the surroundings.