An air conditioner including a heat exchanger according to an aspect of the present disclosure, the heat exchanger includes a refrigerant pipe, and a plurality of fins including a first fin and a second fin spaced apart from each other in an extending direction of the refrigerant pipe, wherein the first fin includes a flat portion and a cut-up member protruding in an arrangement direction of the second fin in the flat portion, and the height of the cut-up member in the extension direction is between 0.5 and 0.7 times the distance between the first fin and the second fin.