A known heat exchanger has a lower rate of blocking the movement of moisture through the joint as compared to a joint bonded with a moisture impermeable adhesive because the corrugated and flat substrates are bonded with thermoplastic fibers by performing heating and pressurizing treatments, but has insufficient moisture permeability because both the flat substrate, which is a partition, and the corrugated substrate, which is a space retaining plate, have a poor moisture permeability.In a heat exchanger in which two types of air flows are directed across a moisture permeable partition plate spaced apart from an adjacent partition plate by a space retaining plate, and perform heat exchange between them through the partition plate, a joint is formed by bonding the partition plate and the space retaining plate using fluoro-resin or hydrocarbon resin containing a hydrophilic group to provide an excellent moisture absorption and diffusion property.