PROBLEM TO BE SOLVED: To provide a disposable (throwaway) heat exchanger allowing easy priming or air bleeding inside a meandering fluid passage, inside a heat exchanger body, and used in hemodialysis treatment or the like.SOLUTION: Partition parts 12P form a meandering fluid passage 12FP extending in a long L direction of a heat exchanger body 12H. The partition parts 12P form a large space 12LS between an upper open part 12OU and an upper part U of the heat exchanger body 12H. The upper part U side of the heat exchanger body 12H is formed with an inclination 12SL ascending toward the upper part U side from a base end PE side to an end DE side. The heat exchanger body 12H is mounted with a fluid inlet 13FI on the upper part U side and on the base end PE side, is mounted with a fluid outlet 13FO on a lower part U side and on the end DE side, and is mounted with an exhaust port 14 on the upper part U side and on the end DE side. A first clamp is mounted close to the fluid outlet 13FO, and a second clamp is mounted close to the exhaust port 14.
