To provide a power-saving friction transmission type driving force distributing device capable of performing driving force distribution control through inter-roller radial pressing force control with small power consumption.

While a part of torque to a main drive wheel via an input shaft 12 is transmitted from a roller 31 on the input shaft 12 to a subordinate drive wheel via a roller 32 on an output shaft 13, crank shafts 51L, 51R are rotated by a motor 58 through a torque diode 61, a gear box 57, and pinions 55L, 55R, and a rotational axis O2 of the output shaft 13 and the roller 32 is turned around an axis O3, and thereby inter-roller pressing force (driving force distribution between main and subordinate drive wheels) is controlled. The torque diode 61 can maintain the inter-roller pressing force at a command value by an irreversible transmission effect during a period while an inter-roller pressing force command value is invariable even when the motor 58 is not operated, and thus the power consumption of the motor 58 can be reduced. In a case requiring no high-precision driving force control such as straight traveling, the motor 58 is driven and controlled by a low resolution command value in which an invariable time of the inter-roller pressing force command value becomes longer.