To provide a method for manufacturing a heat exchanger capable of reasonably brazing tubes of the heat exchanger.

In the method for manufacturing a heat exchanger having a core 10 with tubes 20 and fins 30 layered thereon and a tank body 40 with an end of the tube connected thereto, and capable of performing the heat exchange by the heat of a medium flowing in the tubes, transferred to the core, a plurality of kinds of components are assembled and subjected to the in-furnace brazing. The tubes are provided by brazing the components formed of a strip-like material in the in-furnace brazing. During the in-furnace brazing, by heating a component having the heat capacity larger than that of the tube component in advance during the in-furnace brazing, the difference between the time at which the tube component reaches the brazing temperature, and the time at which the component having the larger heat capacity reaches the brazing temperature is reduced.