A heat exchanger and a fin of the same are provided. The heat exchanger includes a tube, a plurality of fins, a slit section, and a condensed water guide. The tube is arranged in at least a front row and a rear row with respect to a direction of airflow. The plurality of fins is installed with the tube passing therethrough. The slit section is formed on the fins and includes a plurality of slits. The condensed water guide is formed between at least the front row and the rear row, for guiding a draining of condensed water that is generated on a surface of the tube. A fin of the heat exchanger includes a plurality of tube insert holes, a slit section, and a condensed water guide. A refrigerant tube is inserted in the plurality of tube insert holes. The slit section includes a plurality of slits formed around the tube insert holes. The condensed water guide is formed at a rear side of one of the slits, and guides a draining of condensed water generated in a heat exchange process between refrigerant and air.