A heat exchanger includes a main heat exchange unit including a plurality of first heat transfer pipes arranged side by side, a sub-heat exchange unit including a plurality of second heat transfer pipes arranged side by side, and a relay unit including a plurality of relay passages connecting the plurality of first heat transfer pipes and the plurality of second heat transfer pipes. Each of the plurality of relay passages has one inlet connected to a corresponding one of the plurality of second heat transfer pipes, and a plurality of outlets each connected to a corresponding one of the plurality of first heat transfer pipes. Each of the plurality of relay passages distributes refrigerant flowing from the one inlet, without merging streams of the refrigerant together, and causes the refrigerant to flow out of the plurality of outlets.