A controller for a load drive system which can reduce a ripple current which flows in a smoothing capacitor even when an inverter is PWM controlled with a two-phase modulation includes a converter for changing an output voltage of a DC power supply, an inverter for transforming a DC voltage outputted from the converter into a three-phase AC voltage to be applied onto a load and a smoothing capacitor provided in parallel between the converter and the inverter includes an inverter controller for PWM controlling the inverter with a two-phase modulation and a converter controller for PWM controlling the converter.