Provided is a heat exchanger that can, even when frosting occurs on an upwind side of the heat exchanger, exchange heat continuously on a downwind side of a fin by securing a ventilation path, and in addition, further improve drainage of the melt water. The heat exchanger (10) of the present invention includes a plurality of tubes (21) each having a refrigerant flowpath (21a) through which a refrigerant flows and a corrugated fin (22) including a plurality of heat transfer walls (23) that are arranged in a running direction of the tubes (21) and span from one to the other of adjacent tubes among the plurality of tubes (21), the fin being capable of exchanging heat with the tubes (21). Each of the heat transfer walls (23) includes a heat transfer piece (23R(L)) leading to a leading edge portion (23a) positioned on the upwind side of a passing airflow (A) and a leading edge portion (23b) indented toward the downwind side in the direction of the airflow A relative to the leading edge portion (23a). A first heat transfer piece is disposed on every other layer of the arrangement on both of a side closer to one tube (21) and a side closer to the other tube (21) of adjacent tubes among the plurality of tubes such that first heat transfer piece appears alternately on both sides.