PURPOSE: To realize precise connection with ease by cutting bellows opposed to each other in roots thereof, bending thread portions continuous to the cut roots outward to thus form bent portions, superposing the bent portions, and soldering them in connecting the bellows having the same diameter.

CONSTITUTION: In connecting bellows 1, 2 having the same diameter at the opposed ends thereof in the axial direction, the bellows 1, 2 are cut at the roots at the opposed ends and bent outward at right angles in approximately the middle portions of inner erecting portions reaching thread portions 5, 6 continuous to the cut roots, to thus form bent portions 11, 12. A core bar, which is brought into slide-contact with the inner diameter portions of the bellows 1, 2, is inserted into the bellows 1, 2, to be thus aligned along the axis. The bellows 1, 2 are brought into contact with each other so that the bent portions 11, 12 are superposed one on another. Thereafter, solder 15 is poured into a superposing recess 14 between the thread portions 5, 6 holding the superposed portions 13 therebetween, followed by soldering. After soldering work, the core bar is removed, thus completing a connecting bellows which is connected in a coaxial manner.