A sheet metal component, obtained by press-forming a one-piece metal sheet comprised of two metal sheets into a desired shape, has an expanding portion having an external appearance varying in dependence on a weld state of a weld portion of the one-piece metal sheet at which the two metal sheets are welded at their confronting ends. In manufacturing the sheet metal component, the one-piece metal sheet is transferred between upper and lower dies of a pressing machine and is positioned such that its metal sheet section including part of the weld portion is disposed between a punch formed in the lower die and a recess formed in the upper die so as to face the punch. The metal sheet section is pressed by the punch to be subject to plastic deformation, whereby the expanding portion is formed.