PROBLEM TO BE SOLVED: To obtain a heat exchanger having excellent corrosion resistance for an ant's nest-like corrosion by engaging a tube with a fin, and interposing a metal zinc-containing coating film or a zinc-plating layer having a specified thickness between at least engaging interfaces of the engaging part. SOLUTION: The heat exchanger is constituted by inserting a tube 1 via fin collars 3 of laminated fins 2, and engaging the tube 1 with the fins 2. In this case, a metal zinc-containing coating film or a zinc-plating layer 4 having a mean thickness of 1 to 50 μm is interposed between engaging interfaces of the tube 1 with the fins 2. The fin 2 is previously covered on its overall surface with a hydrophilic film 5. Thus, the film 4 containing a metal zinc of a substance having a larger ionization tendency than that of a copper is formed in a gap (engaging interface) in the case of enlarging and connecting the tube 1 to the fin 2, thereby preferentially dissolving the zinc in an acid adhering water to change the water to an alkali side and make it harmless.