A drive power from an engine is transferred to front wheel drive systems and rear wheel drive systems via a central differential. A torque distribution ratio between front and rear wheels defined by the central differential is set to one for the front wheels being made too much thereof, with a motor generator being coupled to the rear wheel drive systems. In response to detection signals from various sensors for detecting the running conditions, a drive power control unit controls the additional torque from the motor generator toward the drive torque or regenerative braking torque side, thereby changing the torque distribution ratio between the front and rear wheels. Thus, a degree of flexibility in making a change in the torque distribution between front and rear wheels or between right and left wheels is increased, thereby realizing an all-wheel drivable hybrid vehicle which provides further improved running performance.