PURPOSE: To secure gaps between respective cut-and-raised pieces sufficiently to increase the heat exchanging efficiently of a heat exchanger without inviting the increase of passing resistance by a method wherein the louver type cut-and- raised piece is bent into a chevron type at the center thereof.

CONSTITUTION: A flat plate type fin 10 is bored with a plurality of heat transfer tube penetrating holes 11 and is formed with a plurality of louver type cut-and- raised pieces 12 between the penetrating holes 11 so as to be orthogonal to the flow direction A of airflow. Respective louver type cut-and-raised pieces 12 are cut and raised so that the front end rims 12 a thereof are raised toward one surface of the fin 10 while the rear end rims 12b thereof are raised toward the other surface of the fin 10. The substantially central part 12c of the fin 10 is formed so as to be biased toward the downstream side of the flow direction A of the air-flow with respect to the boundary of an imaginary plane B connecting the front end rim 12a and the rear end rim 12b. The central part 12c of the louver type cut-and-raised piece 12 is bent so as to have a bent angle β larger than the inlet angle α of the front end rim 12a and is formed so that the sectional surface shows a chevron type configuration.