PURPOSE: To restrain a rising part to fall down inward by providing a flange on an inner panel part side to which the rising part of an outer panel part is formed, among connecting parts between the inner and outer panel parts constituting a side body.

CONSTITUTION: An inner panel part 1 and an outer panel part 2 constituting a side body are placed on a jig, and by connecting both by welding contacted parts the side body 8 in one body is formed. At this time, among connecting parts of the inner and outer panel parts 1,2, a flange 11 with which the rising part 9 to the inner panel part 1 side formed on the outer panel part 2 is restrained to fall down inward, is formed on the inner panel part 1 side. Hereby, the outer panel part 2 is placed on the jig 14, when the inner panel part 1 is brought down from the upside and fitted to the part 2, the side part 11a of the flange 11 is contacted with the rising part 9 on the outer panel part 2 side, and the rising part 9 is restrained to fall down inward.