To satisfactorily supply lubricating oil, and to prevent a ball from wearing and pitching, by forming an oil route through at least one of disk plates in parallel with an axis of the disk plate, in a device which is formed by arranging plural balls between a pair of disk plates.

When a differential case 1 is rotated by driving force transmitted from an engine, a ball holder 4 rotates integrally with the differential case 1, and this rotating force is transmitted to a groove 3b of each disk plate 3 through each ball 5, and to right and left driving shafts connected to each disk plated. At this time, because oil routes 3e, 3f which penetrate through each disk plate 3, and a radial oil groove 3g are formed on each disk plate 3, lubricating oil which is supplied from the differential case 1 is supplied through the oil routes 3e, 3f and the oil groove 3g, and lubricates the interface of the groove 3b and the balls 5. Therefore, wearing and pitching of the balls 5 are effectively prevented.