PURPOSE: To reduce the problem of sealing during expansion of each of axial sections by reducing the diameter of a tubular member between two transmission members while maintaining its wall thickness.

CONSTITUTION: A tubular member 1 is composed of pipe sections 2, 3 having a large diameter, and pipe sections 4 to 6 located therebetween and having a small diameter. Stepped sleeves 7 to 9 are fitted onto the tubular member 1, and are fixed to the sections 2, 3 between the transmission members 10, 11 fixed to these sections. Further, transition parts 13 to 16 are outward conical, toward the transmission members 10, 11, and the bore 12 of the pipe-like member 1 is shifted into inner chambers 17, 18 which are plastically deformed by supply of pressure into the tubular member 1 in order to induce elastic prestress in the transmission members 10, 11 in order to effect configuration coupling. Thus, the tubular member 1 is united.