To suppress the fluctuation of a system voltage by a current zero-cross changing over the polarity of a battery current (a current flowing between a DC power supply and a step-up converter).

The battery current IB is obtained on the basis of an accelerator opening, the sum-up power of first and second AC motors 11 and 12 and a battery voltage VL (the voltage of the DC power supply 13). The generation of the current zero-cross changing over the polarity of the battery current IB is predicted from the behavior of the battery current IB. When predicting the generation of the current zero-cross, the fluctuation of the system voltage VH by the current zero-cross is restrained by correcting the torque command values of the AC motors (one or both of the first and second AC motors 11 and 12) so as to suppress the fluctuation of the system voltage VH by the current zero-cross. A sensor (such as a current sensor) for deciding the current zero-cross need not be mounted anew in this case, and the demand for cost reduction can be satisfied.