PURPOSE: To improve the heat exchanging performance of heat conducting fins of a refrigerant vaporizer by disposing louvers of the refrigerant vaporizer parallelly to the airflow through the space between flat tubes and heat conducting fins, the end of the louvers pointing downward when the refrigerant vaporizer is set in place.

CONSTITUTION: A heat conducting fin 2 has multiple folded-up louvers 20 which are pointing downward in regard to the direction of gravity and are disposed parallelly to the airflow direction A entering into a refrigerant vaporizer. Therefore, the codensate attached to the louvers 20 drops downward by its gravity, and, since they are parallel to the airflow A, the water is easily drained and the louvers 20 have more surface area that is exposed to the ambient air. Further, because of the parallel arrangement with the airflow A, dead water spots are eliminated, and the drafting air is effectively cooled by all of the louvers 20 and heat conducting fins 2. In addition, since the louvers 20 not become the drafting resistance, the airflow rate can be increased, and so, the cooling effect can be improved.