To improve comfortability of a vehicle by providing a carrier supporting an external gear, which is a half of an internal gear in number, freely rotationally and a rotational body supported in a housing freely rotationally while matching its axis line with the rotation axis line of the hous ing and transmitting the rotation of the external gear to the rotational body.

When a housing 2 is rotationally driven, the whole of a device is integrally rotated if equal loads are applied, and output shafts 3A, 3B are rotated at the equal rotational speed. On the other hand, if different loads are applied, the output shaft 3A (3B) whose load is larger is rotated in the direction reverse to the rotation direction, while the output shaft 3B (3A) whose load is smaller is relatively rotated in the same direction as the rotation direction. As the number of teeth of an external gear 7 is set to be a half of that of an internal gear 4, the respective output gears 3A, 3B are rotated in the opposed directions relatively at the equal rotational speed. In the used gear, only two gears, which mean the internal gear 4 and the external gear 7, are used, and gearing is carried out in only a single position, so that rattling due to a backlash between gears can be reduced.