PURPOSE: To provide an apparatus for preventing the putrefaction of especially an emulsion-type oil for cutting, grinding, etc., by placing a basket containing a far infrared radiating ceramic material in a tank for a water-soluble oil and connecting an ozonizer in the basket.

CONSTITUTION: A basket 15 containing a ceramic material 16 capable of emitting far infrared ray of about 6-12μm wavelength is placed in a tank 11 for storing a water-soluble oil 12. Furthermore, an ozonizer 18 to pass ozone near the ceramic material and release into the oil is placed in the basket to obtain the objective apparatus.