When an ECU receives a transmission signal having a high level from a transmission, the ECU exerts torque reduction control to reduce a torque control value for a motor generator. Furthermore the ECU sets an optimum (or target) value of a voltage as based on the torque control value and a motor rotation speed and controls an upconverter. Herein, when the transmission is shifting gears, the ECU controls the upconverter to allow the voltage to be constant regardless of whether the torque reduction control is exerted to reduce the torque control value.