PURPOSE: To provide a butt welded joint having no possibility of breakage in the weld boundary part by providing a step to the butt part of a base metal having the higher creep rate out of different base metals and building up a creep resistant metal by welding to the thin-walled part thereof.

CONSTITUTION: The step 18 is provided to the butt part 14A of a ferrite pipe 14 in the stage of forming the butt joint 16 of an austenite pipe 12 and the ferrite pipe 14, etc. The butt parts 12A, 14A of both pipes 12, 14 are joined by a deposited metal such as "Inconel(R)" 82 having excellent resistance to creep and further the deposited metal thereof is built-up by welding onto the outside peripheral surface of the step part of the pipe 14 to form a build-up part 16A. The creep-resistant build-up part 16 is formed to the outside periphery at the end of the pipe 14 according to such welded joint and therefore even if the pressure in the joint increases, the creep deformation is suppressed and the axial bending stress generated in the part shown by a code A is diminished.