PURPOSE: To improve regeneration efficiency of a thread- and wire-coiled filter of a filtering body produced by coiling cotton threads and shape memory alloy wires together by heating filtering body to the temperature higher than the transition temperature of the shape memory alloy wires of the filtering body to regenerate the filter.

CONSTITUTION: When circulating water flows in through a flowing route 5, detergent components in the circulating water are adsorbed by cotton threads, and dust and particles adhere to the surface of a filtering material 3 as filtration scum and the finer the particles are, the closer the particles go to the filtering core 2 in the inside of the filtering material 3. When water at high temperature is led to the filter through the flowing route 5 after the filter is used for a prescribed period, a temperature sensor 9 installed in the filtering material 3 detects the rise of the temperature and changes the route of the circulating water from a flowing out route 6 to a water discharging route 6 by a switching valve. Further, when the temperature of the filtering material 3 rises and the temperature of the shape memory alloy exceeds the transition temperature, the shape memory alloy contracts and shrinks the cotton threads. As the result, the fine particles enter the inside of the filtering material 3 and the detergent components adsorbed by the cotton threads are pushed out to the outside of the filtering material 3 and discharged through the discharging route 7, and thus the filter is regenerated.