To provide a quiet and compact differential friction roller reduction gear with a high reduction ratio, eliminating the lost of power transmitting ability even if a rolling bearing is worn.

The differential friction roller reduction gear comprises a casing for supporting an input shaft and an output shaft in a concentric and rotatable manner, the input shaft provided with an eccentric shaft being parallel to a center shaft thereof and having a width in an eccentric direction smaller than that in a perpendicular direction, a friction roller having a friction roller surface on the outer periphery and a plurality of through-holes opened in the side face, the rolling bearing provided in a space to the eccentric shaft at the center of the friction roller, a friction inner roller fixed into the casing, force-out means provided between the eccentric shaft and the rolling bearing for putting the friction roller in force contact with the friction inner roller, and an output shaft integrated with a disc on which a transmission shaft is fixed for transmitting torque from the friction roller with the engagement of the through-holes. Therefore, it has quite operation and long power transmitting performance with a high reduction ratio.