The present invention provides a heat exchanger including a lower header into which a liquid-phase refrigerant flows, a plurality of heat exchange pipes which branch off from the lower header and extend upwards, and an upper header which is configured to collect refrigerant received by the heat exchange pipes, in which a refrigerant inlet of the lower header is provided with a flow passage resistance adjusting hole having a cross-section smaller than a flow passage cross-section of a pipe passage for supplying the refrigerant.