A control apparatus for a motor-generator includes a stator including multi-phase coils, a rotor, a multi-phase inverter one arm of which includes a switch element and a free-wheeling element, and a power supply connected between a neutral point of the coils and a negative electrode of the inverter. When the switch elements are driven by rectangular wave, the low-side switch element connected to the high-side switch element is subject to PWM switching control while the high-side switch element is off. When a time point, at which the high-side switch element is turned off, is defined as a base point, if α is defined as a time when switching of the low-side switch element starts, and β is defined as a time when the switching ends, β-α is 120 degrees in electrical degree or more, α is more than 0 degrees, and β is less than 180 degrees.