To provide a filter which prevents the accumulation and propagation of caught microorganisms in the filter and has a high microorganism removing capacity.
A metal net 11 is brought into contact with the nonwoven fabric 12 (filtration means) of the microorganism removing filter using the nonwoven fabric 12 of heat-resistant fibers, and a wire 13 for electric heating is connected to the metal net 11. A noble metal catalyst is supported on the surface of the metal net 11 or the nonwoven fabric 12. In the filter, when the metal net 11 is electrically-heated, The microorganisms caught by the filter are converted into an organic gas. The organic gas is thermally-decomposed into carbon dioxide, water, and nitrogen by the action of the noble metal catalyst. By thermally-decomposing the microorganisms on the filter, the accumulation and propagation of the microorganisms are prevented to prevent the clogging of the filter by the microorganisms.