A boosting switch circuit is constituted by a plurality of MOSFETs of which drains are respectively connected to a plurality of output terminals of an AC magneto and sources are connected to each other or together. The MOSFETs each have a parasitic diode in a drain-source circuit thereof. The parasitic diodes and a plurality of rectification diodes are subjected to bridge connection, to thereby provide a rectifying circuit for rectifying an AC output voltage of the AC magneto. The MOSFETs are fed at a gate thereof with a drive signal of a rectangular waveform, resulting in being concurrently subjected to on-off operation. This permits the output voltage of the AC magneto to be boosted and then rectified through the rectifying circuit. The output voltage thus boosted and rectified is then fed to a load.