A wave-shaped portion 5b, the profile of which is formed into a wave-shape, is provided on the core plate 5, and tubes are brazed to the core plate 5 under the condition that the tubes are inserted into holes 5c formed in bent portions 5a. Due to the above structure, even when a pitch between the tubes is reduced, it is possible to ensure a sufficiently high mechanical strength of the core plate 5. Accordingly, the occurrence of a big difference in the mechanical strength between the core plate 5 and the tubes can be suppressed. Therefore, stress concentration at a joint portion of the core plate 5 and the tubes can be prevented. As a result, the mechanical strength of a radiator and the reliability (durability) of the joint portion of the core plate 5 and the tubes can be enhanced.