To consume a large amount of resources of petroleum or the like necessary for a power source of thermal power, nuclear power, etc., in the present prime mover for generating power, but manufacture a prime mover capable of reducing even a certain degree of the resources thus consumed.

A sliding weight rod 8 or the like is inserted in a radial rotary unit B provided with an output shaft 4, this rotary unit is assembled in a base board A provided with an annular guide rail 2 and an output bearing 1, a rotation assistor D utilizing a spring assisting turning force is mounted in the rotary unit, gravitational unbalance of the weight rod is always generated, the rotary unit is continuously rotated, and a shaft output is obtained.