Abstract: An inside wall surface of a cap covering the end portion of a header tank is formed into a spherical shape, and a connecting portion between the inside wall surface of the cap and a inside wall surface of a tank portion is separated away from a connecting portion between the inside wall surface of the tank portion and an outside wall surface of a tube. Thus, the brazing material is suctioned into both connecting portions (both gaps) sufficiently, and both connecting portions are brazed firmly.