To provide a low-cost differential gear unit of simple structure capable of reducing the viscosity of lubricating oil early by quickening the temperature rising speed of the lubricating oil at a low temperature.

This differential gear unit includes: a housing 11; side gears 21 and 22 rotatably held inside of the housing 11; and pinion gears 23 and 24 rotatably held inside of the housing 11, and interposed between the side gears 21 and 22. The housing 11 includes: one or more recessed holding parts 33 and 34 for rotatably holding the pinion gears 23 and 24; and friction members 36 and 37 arranged between both the recessed holding parts 33, 34 and the pinion gears 23, 24 and formed from a raw material having a coefficient of linear expansion larger than that of the pinion gears 23 and 24 and formed into a nearly semi-cylindrical shape along the outer peripheral surfaces of the pinion gears 23 and 24.