To provide an EGR cooler which has a small number of parts and achieves compact design with low cost. A plurality of flat tubes, each having a bottom to close an end thereof, is arranged in parallel. An opening of each of the flat tubes penetrates through a tube plate. Corrugated fins are placed in each of the flat tubes, thus forming a core. A casing encloses the outer circumferential surface of the core. The tube plate closes the opening of a tank body equipped with a partition. The edge of the partition is placed at an intermediate position in the width direction of the opening of the flat tube.