In an electric motor drive system for an electric vehicle that includes a converter for performing direct-current voltage conversion and an inverter that converts the output voltage of the converter into alternating-current voltage, a control apparatus makes a required torque response determination to determine whether the electric vehicle is in a state in which high torque response is needed. Furthermore, in a drivability priority mode in which high torque response is needed, the control apparatus sets a voltage command value for the converter in a range where sine wave PWM control can be applied. On the other hand, in a fuel efficiency priority mode in which high torque response is not needed, the control apparatus sets the voltage command value for the converter such that power loss in the overall electric motor drive system is minimized, based on the operating state of an alternating-current electric motor.