A heat exchanger includes a fin having a first through hole into which a first heat transfer tube is inserted and a second through hole into which a second heat transfer tube is inserted and including a first end portion and a second end portion, in which a virtual straight line passing through end portions on the first end portion side of the first heat transfer tube and the second heat transfer tube is a first virtual straight line, a virtual straight line passing through end portions on the second end portion side of the first heat transfer tube and the second heat transfer tube is a second virtual straight line, a region between the first end portion and the first virtual straight line is a first drainage region, a region between the second end portion and the second virtual straight line is a second drainage region, and a region enclosed by the first heat transfer tube, the second heat transfer tube, the first virtual straight line and the second virtual straight line is a water introducing region, a first groove inclined to descend toward the first drainage region and a second groove inclined to descend toward the second drainage region are formed in the water introducing region.