PURPOSE: To obviate the need of the forecleaning and after-cleaning for brazing and reduce the manhour for assembly by fitting the edge part of a metal pipe with a connecting metal fitting having an engagement groove in the direction perpendicular to the axis on the inner peripheral surface and carrying out assembly by plastically deforming the part corresponding to the engagement groove by compressing the pipe in the axial direction.

CONSTITUTION: A nipple metal fitting 12 is inserted from the small diameter part 34 side into a fitting hole 22 on a connecting metal fitting body 14. Then, the outer peripheral part of the nipple metal fitting 12 is clamped by a clamper 36, and the connecting metal fitting body 14 is pressed to the clamper 36 side by a working mold 38. At this time, a shaft member 40 is intruded into the nipple metal fitting 12, and the deformation to the diameter contraction direction of the nipple metal fitting 12 is suppressed. Accordingly, the metal fitting 12 is plastic-deformed so as to fill the annular groove 24 on the metal fitting body 14, and the outer surface of the fitting part of the metal fitting 12 is firmly attached on the inner surface of the fitting hole 22 on the metal fitting body 14 and the nipple metal fitting 12 and the connecting metal fitting body 14 are assembled integrally.