PURPOSE: To prevent the deterioration in the material quality and crack in the joint part of a thick wall metallic pipe of a large diameter and a nipple as a joint fitting and to decrease the residual stress therein in the stage of welding said metallic pipe and the nipple by interposing a sleeve between both and welding the two members.

CONSTITUTION: A nipple 2 as a joint fitting is worked to have the inside and outside diameters equal to the inside and outside diameters of a metallic pipe 4 in the stage of joining the pipe 4 and the nipple 2. A sleeve 3 having the outside diameter roughly equal to the inside diameter of the pipe 4 and the nipple 4 and having a projection 3A of the same height as the outside diameter of the nipple 2 and the pipe 4 in the central part is interposed between both and both ends of the sleeve 3 are fitted into the nipple 2 and the pipe 4 in tight contact therewith. The connecting end of the nipple 2, the projecting part 3A of the sleeve 3 and the connecting end of the pipe 4 are beveled to about 30° and are thereafter welded by weld beads 5. The welded juncture having an excellent characteristic is thus formed.