PURPOSE: To catch suspended substances in a liq. to be treated on the surface of a filter material not to make it penetrate into the inside of the filter material, and to remove easily the suspended substances to make the filter material regeneratable by constituting a cylindrical filter with a thermoplastic synthetic fiber and coating the surface with a porous synthetic resin foam.

CONSTITUTION: A cylindrical filter 1 is constituted with a thermoplastic synthetic fiber and the surface is coated with a porous synthetic resin foam 2. In addition, the filter 1 is built in a closed tank 3 and the hollow part of the filter 1 is communicated with a high pressure fluid source 7 and a fitrate outlet pipe 4 through a switch valve. In addition, one end of a stock liq. feeding pipe 5 and a concn. liq. outlet pipe 6 are opened on the closed tank 3 and an air exhausting pipe 8 is also opened on the closed pipe. As a result, the suspended substances of a liq. to be treated are caught by the surface of the filter material so as not to make it penetrate into the inside of the filter material and the caught suspended substances are easily removed to regenerate the filter material.