PURPOSE: To prevent a bather from feeling due to the unpleasantness intrusion of cooling air by arranging at least a part of an air feeding pipe with one end connected to a bathwater feeding pipeline close to an air heating source and utilizing the excess heat to heat the air mixed in the bathwater jet.

CONSTITUTION: An air preheater B is provided to a circulation-type water purifying and warming device A including a filter 18 and a sterilizer, the entire surface of a heater 17 is surrounded by a radiation preventing jacket 23, one end of an air feeding pipeline 21 is communicated with an air heating space 24 between the jacket and the heater 17 through a heated air outlet 25, and the other end of the pipeline 21 is communicated with the introduced air 20 around an injection port 16 opened to a bath. The air heated by the heater 17 in the space 24 is sucked by the air feeding pipeline 21 due to the ejector effect produced when the bathwater is injected from the port 16 by operating a circulating pump 14 and mixed into the injected bathwater, and bubbles are produced in the bath.