PURPOSE: To suppress stress corrosion crack at a weld joint by controlling, through the existence of a cladding by welding, the increase of carbon content in a nickel group alloy steel that forms the weld joint.

CONSTITUTION: In joining a carbon steel member 5 to a stainless steel member through a weld joint 6 consisting of a nickel group alloy steel, a groove face 4a, 5a is provided on the joined end of both members 4, 5; a cladding by welding 9, whose material has less carbon content than the carbon steel member 5 and a slightly higher carbon content than the weld joint 6, is formed on the groove face 5a of the carbon steel member 5. A groove face 9a is provided on the joined end of the cladding 9 and placed opposite to the groove face 4a of the stainless steel member 4; the weld joint 6 consisting of the nickel group alloy steel is formed between the two groove faces 4a, 9a; and the cladding 9 formed on the end of the carbon steel member 5 is firmly joined to the end of the stainless steel member 4.