To provide an apparatus and a method for cleaning a water-soluble cutting fluid to prevent the generation of foul smell by the efficient sterilization of microorganisms in the water-soluble cutting fluid and sufficiently cleaning the water-soluble cutting fluid to prolong its life.

The cleaning apparatus 1 is provided with a cleaning tank 3 composed of a plurality of tanks 17a-17d successively receiving the water-soluble cutting fluid, a skim removing means (oil skimmer 4) to remove the skim on the water-soluble cutting fluid in a skim-collecting tank 17b among the multiple tanks, and an ozone aeration means 5 to introduce ozone into the water-soluble cutting fluid in the 1st aeration tank 17c placed at the downstream side of the skim collecting tank among the multiple tanks. Preferably, the apparatus is further provided with a cutting fluid supplying means 2 to recover the water-soluble cutting fluid from a cutting fluid tank 8 of a machine tool and supply the fluid to the cleaning tank after filtration.