PURPOSE: To aim at the promotion of lightweightiness, by constituting the thickness of a flange part in a way of making it thicker as much as the specified volume than that of a blank, in case of an aluminum wheel made up of an expansible material.

CONSTITUTION: A wheel rim 1 is locked to space between a rim locking upper member 10 and a rim locking lower member 11, and a backup roller 12 is forcibly pressed to an outer side of the wheel rim 1, rotating the rim locking lower member 11. Next, each of working rollers 13 and 14 is forcibly pressed to a flange part 2 and then the thickness of the flange part 2 is increased to be thicker as much as about 50W100% than that of a blank. With this constitution, the thickness of the flange part can be brought to be desired one, thus improvements in strength and lightweightiness both are promotable.