A heat exchange core has a plurality of flat tubes laminated in a thickness direction, each flat tube defining an exhaust gas passage in which the exhaust gas flows. A plurality of coolant flow pass holes are formed in each of the flat tubes, wherein each of the coolant flow pass holes penetrates the flat tube in the thickness direction. The coolant flow pass holes of each flat tube are connected with the coolant flow pass holes of the other flat tubes, in order to respectively form a plurality of coolant flow passages through which liquid coolant flows, and the coolant flow pass holes of each coolant flow passages are communicated with each other in the laminated direction, so that the coolant flow passages are formed to be perpendicular to the exhaust gas passages.