PURPOSE: To recover the filtrating function of a filter, by converting dusts having clogged a filter to a conductor by impregnating the dusts with electrolytic solutions, charging the filter with electricity, and generating a strong magnetic field by means of a superconductor coil to dislodge the dusts.

CONSTITUTION: A filter apparatus are composed of a filter 8 comprising nonconductors having pores, a device 14 for supplying electrolytic liquids, superconductor coils 11, 12 disposed close to the filter 8, a pair of electrodes 9, 10 provided at opposite ends of the filter 8, and a D.C. power source 13 connected to said electrodes, wherein dusts having clogged the filter 8 are impregnated with electrolytic solutions so that said dusts are converted to conductors and the filter 8 is electrified, and, further, strong magnetic fields are generated by means of the superconductor coils 11, 12 to produce a Lorentz force on the dusts themselves so that the dusts having attached to the pores of the filter 8 are dislodged, causing the filter to effect its filtrating functions again.