PURPOSE: To improve the air tightness of the soft solder joined part by providing a ring-shaped bulged part penetrated with small holes at the vertex to near the central part of the joining part outside pipe of the joint and beforehand fitting a soft solder material in a ring shape to the inner side of the bulged part.

CONSTITUTION: At the time of joining stainless steel pipes, a ring-shaped bulged part 3 is provided to near the central part of the joining part outside pipe 1 of a stainless steel pipe or stainless steel made joint, and one or a plurality of small holes 4 through which gas or air passes are pierced through the portion near the vertex of the bulged part 3. A soft solder material 5 is beforehand fitted in a ring shape to the inner side of the bulged part 3, thence a joining part inside pipe 2 is inserted and the solft soldering is performed in a preplaced filler metal system. Then, the gas produced at the soft soldering is released to the outside through the small holes 4 and when a negative pressure is developed in the bulged part 3 at the cooling, outside air is flowed therein through the small holes 4; therefore the joined part of good air tightness may be obtained.