A heat exchanger includes: a header that extends in a first direction; and a plurality of heat transfer tubes that extend in a second direction crossing the first direction, each of which has one end connected to the header, and that are arranged in the first direction at intervals. The header includes: a header body having a tubular shape, a first member through which the one end of each of the heat transfer tubes extends, and a second member positioned between the header body and the first member in the second direction. The second member includes: a base portion that extends in the first direction, and a plurality of protruding portions that extend from the base portion toward the first member in the second direction.