MANUFACTURING METHOD OF DIFFERENTIAL DEVICE

A first abutting surface, a first welding surface, a first facing surface are formed in a differential case. A second abutting surface, a second welding surface, and a second facing surface are formed in a differential ring gear. In an installing step, the first abutting surface and the second abutting surface are inserted, positions of the differential case and the differential ring gear are determined in an axial direction, a separation portion that spaces the first welding surface and the second welding surface away from each other and that has a non-linear portion is formed, and a void is formed between the first facing surface and the second facing surface. In a welding step, a laser is irradiated to the separation portion and the first welding surface and the second welding surface are welded.