To prevent any crack from being produced owing to thermal fatigue of a heat radiation fin.

A heat exchanger 10 includes thereinside an inner tube 11 for flowing EGR gas, an outer tube 12 surrounding an outer periphery of the inner tube 11, separated therefrom and defining a communication section 13 of cooling water between it and the inner tube 11 and a heat radiation fin 16 accommodated in the inner tube 11. In the heat radiation fin 16, an end portion E not brazed and fixed to the inner tube 11 function as thermal stress absorption means. An end portion of the heat radiation fin 16 is folded inwardly in a radial direction to form a folded section 18. The folded section constructs thermal stress absorption means.