PURPOSE: To extend the useful life period of a heat exchanger by combining with a tube material by coating a fluoride flux only on a fin material and after holding it under the specified conditions in a Zn vapor deposition, and executing its brazing.

CONSTITUTION: A core 5 is formed by assembling the fin material 2 on which a fluoride flux is dried by coating and the tube material 1 on which no flux is coated. Then after preheating the core 5 in a preheating zone 8 by placing it on an endless mesh belt 7 it is transferred in order to a brazing zone 9 and cooling zone 10. In the zone 9 the Zn vapor treatment of the temp. ≤ the flux m.p. and ≥ the temp. of the member 5 is executed for ≥1min. Since the fluoride flux is coated on the fin material 2 only, the Zn deposition restraining action of the flux film is prevented. The useful life term of a heat exchanger is extended because of the Zn deposition efficiency being improved.