Abstract: A flywheel power source device for converting electric energy into kinetic energy and for storing the kinetic energy by rotating a flywheel of which rotary shaft is rotatably supported by a bearing mounted in a casing at high speed, wherein the kinetic energy is reconverted into electric energy when necessary; the flywheel power source device is provided with a rotational fulcrum at a bottom of the rotary shaft and a center of gravity of the flywheel being positioned on a line of action of a resultant force of magnetic attractive forces acting on the flywheel.