PURPOSE: To extensively select distribution ratio of output by inputting a troque through an outside case as well as supporting an epicyclic gear of an epicyclic gear set and by constituting an internal gear and a sun gear to output torque from one side of an output axis nd from the outside respectively.

CONSTITUTION: The driving force from an engine is transmitted to an inner bearing 61 and a sun bearing 63 through an outside case 31, a carrier 67 and an epicyclic bearing 65 supported by a transmission case 37 free to rotate by bearings 33, 35, and differentially distributed respectively to a front wheel side and a rear wheel side through output axes 47, 45 by the autorotation of the epicyclic bearing 65. Torque is transmitted to the rear wheel side through the inner bearing 61 and to the front wheel side through the sun bearing 63, and consequently, its distribution ratio is large for the former and small for the latter. As torque is thus inputted from the epicyclic bearing 65, the torque distribution ratio between the front and the rear wheels can be widely gained by way of changing the number of teeth of each of the bearings 61, 63 and 65.