A device for driving a vehicle is provided with an engine (11) serving as the power source for the vehicle and a transmission (12) connected to the engine (11). The engine (11) and the transmission (12) are laterally disposed so that the axial direction of the output shaft of the engine (11) is oriented in the lateral direction of the vehicle. The driving device is provided with a motor generator(MG) (16) serving as a power source for the vehicle and a decelerator (17) connected to the MG (16). At least some of the decelerator (17) and the MG (16) are disposed on the outside of an engine compartment accommodating the engine (11) and the transmission (12). The output shaft of the decelerator (17) is linked, so as to enable power transmission, to a powertrain for transmitting the power fromthe output shaft of the transmission (12) to drive shafts (14) of wheels (15).