To vary the revolution of a two-phase induction motor freely, without the use of a capacitor and improve the drive efficiency of the motor easily.

An inverter 15 which has a plurality of circuit switching means, constituted of a first switching unit 20 and a second switching unit 21 which are connected in parallel to each other, first and second DC power supplies 12 and 13 constituted of two DC power supplies which supply powers to both the terminals of the first and second switching units 20 and 21 of the inverter 15 and are connected in series to each other and inverter control units 16 and 41 by which switching devices 14a-14d of which the first and second switching units 20 and 21 are constituted are controlled individually to drive are provided.