A plurality of heat transfer pipes (8) have a circumferential portion (81) arranged at a short distance from an inner surface (72) of a heat exchanger case (70) while they are bundled to form a pipe group (80) and a first bowstring-shaped portion (82) which retracts toward a center in a direction of cylinder diameter from an arc formed by the circumferential portion (81). The plurality of bundled heat transfer pipes (8) are loaded in a cylindrical core (70) such that the first bowstring-shaped portion (82) and an inner surface (72L) of the cylindrical core (70) on a side where a heat exchange medium inlet port (74) is attached are opposed to each other. By making a flow of a heat exchange medium to each heat transfer pipe (8) uniform, a heat exchanger capable of obtaining high heat exchange performance is obtained.
