To provide a forming method capable of reducing the weight of a wheel disk without impairing the appearance.

In a first forming step, a center disk part 4, an annular main projecting part 5 which is continuous to an outer circumference of the disk part 4 and projected downwardly, and an annular hat part 12 which is continuous to an outer circumference of the main projecting part 5 and projected upwardly are obtained by forming a flat plate-like work, and a plurality of pairs of sub projecting parts 5a which are formed separately in the circumferential direction and projected upwardly are obtained at a bottom part of the main projecting part 5. In a second forming step, a hub fitting part is obtained by squeezing inner circumferential walls of the disk part 4 and the main projecting part 5, and a material of an annular part located on a boundary between the hub fitting part and the hat part and in a vicinity thereof is increased, and a plurality of pairs of locally material-increased parts separate from each other in the circumferential direction are obtained at the annular part by squeezing the sub projecting parts 5a. In a punching step, hub holes are formed in the hub fitting part, and bolt holes are formed on the reference lines L passing through the center of each hub hole and passing through parts between the pairs of locally material-increased parts.