To improve lubrication performance without reducing a sliding area of a clutch plate.

Cutouts are formed on fitting parts of inner plates 28 constituting multiple disc clutch mechanisms 25 and 26. By the cutouts, spaces are formed between the cutouts and mounting grooves 23 when the inner plates 28 are mounted in the peripheries of side gears 20 and 21. A lubricant supplied into a differential case 11 from first lubrication supply holes 15 bored in first and second cases 11a and 11b reaches the peripheries of the side gears 20 and 21 and is thereafter supplied to sliding areas of the plurality of inner plates 28 through the spaces.