<p>A heat exchanger (100) includes: a heat exchange unit (10) having a plurality of fluid paths (13, 14) arranged adjacent to each other and through which a high-temperature coolant and a low-temperature coolant flow; and a header unit (20) attached to both ends of the heat exchange unit (10) so that the high-temperature coolant and the low-temperature coolant flow inside. Two or more heat exchange units (10) of the same configuration are stacked in the longitudinal direction of the header unit (20). This improves the layout in an engine room and improves the workability.</p>
