Abstract: A heat exchanger is made of a metal such as aluminum and for use in the air conditioning apparatuses such as the car coolers and the room air conditioners. A coolant inlet pipe (6) has an end which is forced into a pipe insertion bore (10) of a pipe joint (8) for connection to an external piping, with a cylindrical brazing agent piece (15) being interposed between the outer periphery of the inlet pipe end and the inner peripheral wall of the bore, such that the pipe (6) is brazed integral to the joint (8) by means of the cylindrical piece (15). This cylindrical brazing agent piece (15) is composed of a core layer which has an outer and inner surfaces clad with a brazing agent layer. The pipe (6) and the joint (8) can be preassembled without failing to interpose between them the brazing agent piece (15), so that said pipe and said joint can be brazed one to another surely and at a lowered cost.