PURPOSE: To effectively circulate and filter the withdrawn water or sucked water by passing the water through a filter device in which useful bacterium spore-contg. compds., silica sources and magnesium sources are packed in the case the waste materials included in the water in a tank is subjected to a cleaning treatment and is cyclically used.

CONSTITUTION: The withdrawn water or sucked water is passed through the filter device in which the useful bacterium spore-contg. compds., silica sources and magnesium sources are packed, by which the water is circulated and filtered in the case the waste materials included in the water in the tank is subjected to the cleaning treatment and is cyclically used. A net container 5 is housed in a cylindrical container 4 provided with a withdrawn water introducing port 2 in its bottom and a filtered water delivery port 3 in its cap part, respectively, of, for example, a small-sized filter 1 to be built in a thermostatic purifying device, etc., for home baths. Calcite, zeolite, ceramic balls, granite porphyry and non-woven fabric filter are packed successively from below into the net container 5. Useful bacteria, etc., are implanted on the surfaces of the respective packing materials and the water is thereby filtered.