A filter device has a filter element made from a filter hose that has a filter wall separating an unfiltered side from a clean side of the filter device in a radial direction. In preferred embodiments the filter wall of the filter hose is provided with a very fine particle filtration layer including nanofibers. The diameter of the nanofibers is less than one micrometer. The nanofiber layer can be applied to a green filter material and the filter element can be produced subsequently from the filter material with applied nanofiber layer. Alternatively, the nanofiber layer can be applied to a finished filter element.