PURPOSE: To effectively regenerate a water-soluble cutting agent without detriment to its performances, by heat-sterilizing by introduction of steam.

CONSTITUTION: Steam is introduced into a water-soluble cutting agent which has long been used and emits an offensive smell due to bacterial growth, and the cutting agent is sterilized at 50W90°C. According to the above process, an offensive smell can be eliminated and, on the other hand, oily contaminants brought in during use float to the surface and are removed easily, so that economical regeneration of the cutting agent is possible.