A transfer mechanism distributes drive power from a drive power source of a motor vehicle to left and right front wheels and left and right rear wheels of the vehicle. A rear differential mechanism transfers the drive power to the left and right rear wheels. A clutch is provided between the rear differential mechanism and each of the left and right rear wheels. A control device independently controls an engaged state of each of the clutches. A speed-increasing mechanism sets revolution speeds of an output shaft of the transfer mechanism and of an input shaft of the rear differential mechanism to be the same and sets a speed of the outer circumference of the rear wheel to which the drive power is transferred, via an engaged clutch, to be faster than a speed of the outer circumference of the left and right front wheels.