To prevent the deceleration of a vehicle with the structure that after starting the vehicle with the only electric generator by starting the engine for rotation while a final reduction gear and an engine and an electric generator are separated in a transmission.

The predetermined car speed value V0 is set at a value slightly higher than the car speed value when an automatic transmission 4 is set at the second stage and the speed of an engine 1 is the idle engine speed. When the car speed V is higher than the predetermined car speed V0, the number of revolution of a motor/generator 2 is set zero, and a direct drive clutch 36 is fastened when the terminal reduction gear 20 and the engine 1 and the motor/ generator 2 are separated by a one-way clutch inside of the automatic transmission 4, and the motor/generator 2 is normally rotated so as to start the engine 1 for rotation. When the car speed V is lower than the predetermined car speed value V0, the direct drive clutch 36 is released, and the motor/generator 2 is reversely rotated so as to start the engine 1 for rotation. The one-way clutch 35 is fitted to the periphery of a flywheel FW.