This invention provides a welding method capable of forming on a weld of the material to be welded and in the vicinity thereof in the step of welding a passivated chromium oxide film an outer surface of which has excellent corrosion resisting, a capability of substantially preventing the adsorption of water onto the outer surface, and a capability of permitting water, even when it is adsorbed onto the surface, to be removed simply with low energy; and a welded structure having the same film. A welding method for forming a passivated chromium oxide film on a weld of each material to be welded, consisting of the steps of forming a chromium-containing film at the end of the material which has on its outer surface a passivated oxide film formed by thermal treatment and containing chromium as the main component, setting face to face with each other the ends of the materials thus coated, and welding these ends, whereby a passivated oxide film containing chromium oxide as the main component which has a high corrosion resistance and which does not substantially provide outgassing can be formed on the outer surface of the weld.