A heat exchanger includes heat transfer tubes and a header that forms a refrigerant flow path. The header includes: a first member that includes a first plate-shaped portion; a second member that includes a second plate-shaped portion; a third member that includes a third plate-shaped portion positioned between the first plate-shaped portion and the second plate-shaped portion in a first direction that is a direction in which the first plate-shaped portion and the second plate-shaped portion are arranged; a fourth member that includes a fourth plate-shaped portion positioned between the first plate-shaped portion and the second plate-shaped portion in the first direction and a second opening that constitutes a part of the refrigerant flow path, where a second is along a longitudinal direction of the second opening; and a fifth member.