PURPOSE: To improve the efficiency of a windmill and make it simple and light, by protruding blades in prescribed directions from the edges of the windmill body shaped as a triangular prism and supported by a shaft in the center of the body.

CONSTITUTION: Blades 11 are protruded at prescribed angles in prescribed directions from the edges of a windmill body 6 shaped as a trianguar prism and supported by a shaft 12 in the center of the body. According to this constitution, the blade 11 which returns to the windward is present in the region of rotation of the body 6 and the blades 11 extend almost in parallel with the direction of wind. As a result, less resistance is received and the efficiency of the sindmill is improved. The frame of the body 6 can be made of pipes or the like to make the windmill simple and light.