A heat exchanger includes: a stacked core formed by stacking a plurality of unit plate members in each of which passage formation portions are formed independently of each other to extend from a heat-exchange passage formation portion along a plane; a case formed in accordance with the outer shape of the stacked core, and which houses the stacked core such that heat-exchange media flow into and flow out of the stacked core; and a join portion that serves as a sealing mechanism that supports the stacked core such that the stacked core does not contact the case, and that forms a heat-insulation layer between the case and the stacked core, wherein the heat-insulation layer is a closed space separated from the outside.
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