An electric power converter apparatus incorporates a plurality of electric power converter circuits having respective output terminals connected in common, with output power being produced from the common output terminals. Each converter circuit uses an identical switching frequency, in executing power conversion based on PWM control of switching by a plurality of switching elements. The switching operations of the respective converter circuits mutually differ in phase, by an amount determined in accordance with the currently applied PWM duty ratio. The phase difference value is predetermined for minimizing the amplitude of specific harmonic frequency components of a ripple current component in the output current from the apparatus.