A power supply device includes a failure determination means that detects, based on a current detected by a current detector, a failure of the switching elements of each of the chopper sections, and the failure determination means obtains values of the current detected by the current detector at the timing of falling edges of control signals to the switching elements of each of the chopper sections, determines the failure when the obtained current values differ from each other, and transmits a failure signal to a generation control means. When receiving the failure signal, the generation control means limits an output current from a generator in a way such that the withstanding current of a non-failed chopper section out of the chopper sections of the phases is not exceeded.