Disclosed is a louver fin type heat exchanger positioned upright at a certain angle with respect to the ground, wherein lower end portions of louver fins close to the ground are bent toward lower end portions of adjacent louver fins, such that the air passage at the lower end portion close to the ground has cross-section areas that are wide at certain portions and are narrow at other portions thereof. Accordingly, moisture congregates only at a portion where the cross-section of the air passage is great, so that the external air smoothly passes into or out the heat exchanger through the air passage where the moisture congregation does not occur, minimizing the pressure drop, and efficiency in heat exchange of the heat exchanger can be thusly improved.