PURPOSE: To easily bend a header with a simple structure by bending an assembly immediately before arriving at a brazing temperature in the step of manufacturing a heat exchanger to be brazed by heating the assembly.

CONSTITUTION: An all aluminum assembly 11a is sufficiently heated to be softened upon rising of a temperature in a furnace while a jig unit 21 for placing the assembly 11a of a heat exchanger 11 is sequentially moved from an inlet toward an outlet in the brazing furnace. When the temperature in the furnace reaches a temperature immediately before the brazing temperature such as 550°C, a latch 25 is thermally deformed, and its free end is tilted. Thus, supporting of the free end of a pedestal 23b is removed, it is tilted around a pin 24, and an outer end is dropped in an inner bottom of a jig 22. Thus, both one ends of a pair of headers 12a, 12b placed on the tilted pedestal 23b are tilted by own weights, and bent substantially in an L shape. Then, when it reaches the brazing temperature, it is brazed to predetermined positions of the assembly 11a.