The technique of the invention sets a control start revolution speed Nstart to decrease with an increase in driver's power demand P* and with an increase in vehicle speed V (step S130), and motors an engine (steps S150 to S190). When a revolution speed Ne of the engine reaches the setting of the control start revolution speed Nstart, operation control of the engine starts (step S220). Such settings are ascribed to the following reasons. Setting a relatively small value to the control start revolution speed Nstart is preferable to trigger an early start of operation control of the engine and ensure quick output of power from the engine. In order to ensure reduction of vibrations of initial explosion and resulting reduction of potential vibrations arising at the time of starting the engine, on the other hand, setting a relatively large value to the control start revolution speed Nstart is preferable. The driver's sensitivity to the vibrations is lowered with an increase in vehicle speed V.