PURPOSE: To obtain a heat exchanger capable of uniformly heating or cooling a fluid to be treated by extending in a virtually spiral way in a single flow channel a heating tube arranged inside each of heating medium jackets and by surrounding the tube with plural heating jackets.

CONSTITUTION: A heating medium is fed from a heating medium feed pipe 16 to each of heating medium jackets 12 and discharged from each of the jackets 12 through a heating medium discharge pipe 18. A heating tube 14 is arranged inside each of the heating medium jackets so as to allow a fluid to be treated to pass through and extended in a virtually spiral way in a single flow channel and then surrounded with plural heating jackets.