A heat exchanger is provided which has: multiple flat heat transfer pipes configured such that refrigerant for heat exchange with air flowing inside; and a fin having a heat exchange surface between adjacent ones of the heat transfer pipes, wherein the multiple heat transfer pipes are arranged such that flat portions of the heat transfer pipes face each other, the fin has one end and other end in an air flow direction, and a first rib formed vertically above the flat portion, and the first rib has an extension portion extending along the flat portion, and an enlarged portion configured such that a distance to the flat portion gradually increases from the extension portion in a direction of one end side.