To improve exhaust performance by controlling an acceleration assist amount by an electric machine according to the state of a catalyst.

The activating condition of the catalyst 20 that purifies the exhaust gas of an engine is detected from the temperature of engine cooling water, and the acceleration assist amount by a motor generator 2 relative to an acceleration operation amount is increased as the activating condition of the catalyst 20 is lowered. When the charge of a battery 32 becomes low, the acceleration assist amount by the motor generator 2 is restricted.