To solve the problem that a heat exchanger made of aluminum uses many complicated aluminum materials or alloys, a supply source is easily restricted, and a processing method is precise, and equipment or tooling such as a jig or a tool or a mold requiring high exclusiveness and a large investment is necessary.

The aluminum hollow material 1 manufactured by the most general and widely used extrusion method among processing methods of aluminum is used as the header material. A long hole in a dimension into which a tube 4 is inserted is continuously opened on a side to which the tube 4 is inserted by the widely used cutting equipment, cutting is performed in the prescribed dimension, and the tube 4 having a brazing material on an outer surface is inserted into the opened long hole, and the whole is assembled by brazing. Accordingly, the tooling investment cost of the jig, the tool or the mold for each of product models can be suppressed in an ignorable range, the header material can be supplied from anywhere without having special restrictions to the supply source, and recyclability is improved, and stable quality with time can be secured.