PURPOSE: To surely braze an inner fin to the inside of a tube body, and to surely braze the tube body to a corrugated fin.

CONSTITUTION: An aluminum sheet, on one surface of which a brazing material layer 41c is formed, and on the other surface of which a sacrifice corrosion layer 41b is formed, is bent at the central part thereof so that the brazing material layer 41 is located outside, and both edge parts 41d are opposed to each other, and thus a tube body 41 is formed. Recessed parts 41e are formed on both sides of the tube body 41, being opposed to each other. One side of an inner fin 43 made of aluminum, on both surfaces of which the brazing material layers 43b are formed, is brazed between the edge parts 41 and the other side thereof is brazed between the recessed parts 41e.