To realize miniaturization, weight reduction and cost reduction by making high-frequency chopper operation which enabling semiconductor switching element.

A step-down chopper 20, constituted of a semiconductor switching element 201 of a monopolar type MOSFET or the like, a winding 221 and a diode 212, and a step-up chopper 21 constituted of a semiconductor switching element 211, a winding 222 and a diode 202 are connected in specified polarities between an input side voltage smoothing capacitor 23a and an output side voltage-smoothing capacitor 23b. An iron core is used in common by the windings 221 and 222, or an output is taken out from the center tap 22s of the windings. As a result, current smoothing reactors 22, 22a and further a power converter as a whole are miniaturized.