PURPOSE: To decrease the sensitivity to stress corrosion cracking in the heat affected zone of weld metals by irradiating a heat source of high energy density to the surface of base metals including the weld zone thereby performing solution treatment of the surface.

CONSTITUTION: Base metals 1 consisting of a stainless steel are welded and joined by a weld metal 2. A heat source of high energy density (for example, laser light 5) is irradiated to the surface of the base metals 1 including the weld heat affected zone 3 generated around the weld metal 2. The surface layer of the base metals is thereby performed solution-treatment to form a solid solution layer 10. The sensitivity to stress corrosion cracking in the weld heat affected zone 3 is thus decreased.