Abstract: The purpose of the present invention is to provide an electric generator which allows the magnitude of mutual magnetic action between a rotor and an armature to be self-adjusted in the electric generator against a fluctuation in a motive power or a fluctuation in an electric load, such that the magnitude of an induced electromotive force is controlled to compensate, with voltage variation, for amounts of the fluctuation in the motive power and the fluctuation in the electric load and to induce electricity with a uniform frequency from the electric generator, while stabilizing the prime mover or load devices, and parts optimized for the same.