Provided is a heat exchanger. The heat exchanger includes a refrigerant tube through which a refrigerant flows and a fin having at least two tube through holes in which the refrigerant tube is inserted. The fin includes a fin body, a plurality of louvers protruding from a surface of the fin body, a plane part defined between the plurality of louvers, the plane part having a flat surface, and a guide part disposed on at least one side of the plane part to guide a flow of air or discharge of defrosting water.