Disclosed is a heat exchanger including: a plurality of tubes through which refrigerants flow, the tubes being spaced away from one another; and a fin through which the tubes are perpendicularly inserted, and having a fin collar for supporting the inserted tube, a seat for supporting an outer circumference of a lower end of the fin collar, and three or more peak portions and three or more valley portions that are alternately disposed at an area defined between the tubes to cause air flow to vary at an area defined between the fin collar, heights of at least two peak portions or depths of at least two valley portions being different from each other.