PURPOSE: To improve the heat transfer efficiency of the title heat exchanger by a method wherein a plurality of cutouts are formed in a heat transfer fin attached to a heat transfer tube and the parts of the fin among the cutouts are made to form corrugated shape in an alternative fashion with respect to the surface of the fin.

CONSTITUTION: A number of cutouts 13 are formed in the heat transfer fin 11 and the parts of the fin 11 among the cutouts 13 are made to form corrugated shape in an alternative fashion layer on the surface of the fin 11 becomes thin and the surface are of heat transfer of the fin 11 increases by the surface area of the corrugated P-Q section 1 to thereby increase the heat transfer efficiency of the heat exchanger.