PURPOSE: To improve joining strength and joining quality by fixing the space among plural metal parts by the substance of small thermal expansion coefft. and executing brazing.

CONSTITUTION: The respective metal part 1 adjoining in a room temp. state is assembled in advance by the part 3 having small thermal expansion coefft., screw 4 and nut 5. A brazing filler metal 2 is then arranged at the joining part of the metal part 1 and heated inside a high temp. vacuum furnace. In this case, the brazing filler metal is melted under high temp., the space between parts 1 is filled and the play between parts 1 is reduced by the thermal expansion difference between parts 1, 3. The mutual parts 1 is thus subjected to brazing at the optimum intervals. Consequently the joining strength of the parts 1, 1 is increased, the brazing having no generation of a leak, etc., is executed and the joining strength and quality of the metal part 1 are improved.