Sections 1 and 2 each in the form of a welded pipe (square pipe) are provided. The sections 1 and 2 are brought into abutment with each other so that the respective end faces 3a and 3b abut each other at a predetermined angle .beta. between each section and its axial direction. The sections 1 and 2 are arranged symmetrically with respect to each other. Acute end portions of the abutted portion are chamfered to from a plane part. Corners of the sections 1 and 2 are rounded. In such a combined state of both sections, the abutted portion is welded in the circumferential direction to form a weld bead. As a result, penetration of weld metal to the section 1 and that to the section 2 become equal to each other. Thus, it becomes possible to fabricate a welded structure having a uniform weld bead and having improved strength and reliability of welded portions.