An input shaft that transmits torque to rear wheels is formed integrally with a first roller. An output shaft that directs torque to front wheels is formed integrally with a second roller. An inter-roller-axis distance is set smaller than a sum of semidiameters of the rollers, so as to press the rollers 31, 32 in a radial direction into pressing contact with one another, so that a part of torque from the input shaft to the rear wheels is directed through the rollers and the output shaft to the front wheels. The inter-roller-axis distance is set so as to set an inter-roller radial pressing force so that a maximum distribution condition maximum roller-transmitted torque under a front wheel torque maximum distribution condition, which is determined by the radial pressing force, is below a front wheel maximum distribution torque based on an assumption that a maximum torque is transmitted to the input shaft under the front wheel torque maximum distribution condition.