Heat Exchanger with Catalyst

A heat exchanger with catalyst is provided with a plurality of cooling membrane portions for circulation of cooling water, which are piled up and communicated with each other, first tank portions respectively communicated with first ends of the cooling membrane portions, second tank portions respectively communicated with second ends of the cooling membrane portions, cavities respectively held between the cooling membrane portions, fins disposed in the cavities and an air flow path communicating with the cavities. The first tank portions are communicated with each other and the second tank portions are communicated with each other. The reformed gas flows through the cavities. The catalyst is supported on the respective fins. The air supplied from an outside and the reformed gas are mixed in the cavities and oxidized on the catalyst.