A heat exchanger includes: multiple flat tubes that extend in a second direction intersecting a first direction which is an air flow direction and that are disposed at intervals in a third direction that intersects the first direction and the second direction; and multiple plate-like heat transfer fins that extend along the third direction and that are disposed at intervals along the second direction. The heat exchanger causes refrigerant in the flat tubes to exchange heat with the air flow that passes through heat exchange spaces formed by adjacent flat tubes and adjacent heat transfer fins when viewed from the first direction. The heat transfer fins each have a heat transfer fin front side surface that is one main surface, a heat transfer fin back side surface that is the other main surface.