To provide a differential gear using steel balls available at a low cost, as improvement of a conventional one using bevel gears which is fabricated easily in structural terms, but suits neither mass production nor the practical application because of high price.

A steel ball holding plate 10 formed rigidly to a housing and having a plurality of holes where steel balls 11a and 11b are placed, is installed between circular discs 9a and 9b arranged facing each other at the ends of shafts 8a and 8b penetrating shaft holes bored in the bottoms of two cup-shaped housing halves 1a and 1b, and springs 12a and 12b are set between the housing halves and the discs for pinching the steel balls, and the housing halves are combined and fastened to press the discs by the pressure of the springs so as to generate a slip friction between the steel balls and the two circular discs. As the housing and the steel ball holding plate are consolidated, turning the housing causes the steel balls to be pulled by the plate to trail, and the two discs rotate together, and when either disc stops, the steel balls start rolling on the stopped disc. This rolling motion is transmitted to the counter disc in free rotation to cause its rotating, and thus a differential effect generated.