To provide a differential unit of a model car which blocks an increase in frictional resistance between friction rings and a group of spheres by eliminating the warping deformation of the friction rings.

The differential unit is obtained by: attaching a differential gear 12 to an axle 11 having a wheel 14 fixed to its one end; arranging sphere fitting holes 13 at the differential gear 12 at regular intervals in a peripheral direction; fitting a sphere 19 to each fitting hole 13; abutting a friction ring 21 provided on the side of the axle 11 on one side of the group 19 of the spheres; abutting a friction ring 26 provided at a transmission sleeve 20 sleeved on the axle 11 on the other side of the group of the spheres; fixing a wheel 15 to the other end of the transmission sleeve 20; pressurizing the transmission sleeve 20 to the side of the differential gear 12; and press-contacting the friction rings 21 and 26 respectively with both of the ends of the sphere 19. A plurality of the fitting holes 13 consists of a plurality of kinds of holes having different lengths from the center of the differential gear 12 to the centers of the holes 13.