Provided is a heat exchanger including a plurality of refrigerant flow paths each being a flow path into which refrigerant flows in a gas state and out of which the refrigerant flows in a liquid state, and including upstream-side flow paths allowing passage of the refrigerant in the gas state and a two-phase gas-liquid state, and at least one downstream-side flow path allowing passage of the refrigerant in the two-phase gas-liquid state and the liquid state. The heat exchanger further includes an upstream-side heat exchanger including the upstream-side flow paths, a downstream-side heat exchanger including the at least one downstream-side flow path, and at least one merger for merging the refrigerant flowing out of each of the upstream-side flow paths and causing the merged refrigerant to flow into the at least one downstream-side flow path. The upstream-side heat exchanger and the downstream-side heat exchanger are configured separately. The number of the downstream-side flow paths is smaller than the number of the upstream-side flow paths.