A heat exchanger includes a first flow path through which a first fluid flows, a second flow path through which a second fluid flows, and an adjustment layer disposed between the first flow path and the second flow path adjacent to each other and that adjusts an amount of heat exchange between the first flow path and the second flow path. The adjustment layer includes a first portion and a second portion having a heat transfer performance lower than that of the first portion, and has a heat transfer performance varied depending on a position in the adjustment layer.