A differential case is comprised of: an outer peripheral wall cylindrical about a first axis; a first side wall being perpendicular to the first axis and having a flange; a second side wall having an outer side surface perpendicular to the first axis and being opposed to the first side wall; and an opening opened on the outer peripheral wall so as to allow side gears to be brought in the opening, the opening being so shaped that outlines of pinion gears do not touch a periphery of an oval as an outline of the opening in a case where an axis of the pinion gears is aligned with the center of the oval.