A filter device has a filter housing (1) with a fluid inlet (13) for raw fluid, with a fluid outlet (3) for filtrate and with at least one one-piece or multi-piece filter insert (5, 7) received in the filter housing (1). The filter insert can be cleaned using at least one back-flushing member (21) in counter-current to the filtration direction. This back-flushing member can, by a fluid-guiding driveshaft (23) of a rotary drive (35), be moved along the inner side (19) of the respective filter insert (5, 7) and has, at its end adjacent to this inner side (19), a gap-shaped passage opening (39) that extends parallel to the axis of rotation of the driveshaft (23) and that discharges into a flow space (41; 57; 67) fluidically connected to the driveshaft (23). The flow space at least partially continuously narrows in the direction of the driveshaft (23) in a first plane in which the passage opening (39) lies. In another second plane transverse to the first plane, the flow space (41; 57; 67) at least partially continuously widens proceeding from the passage opening (39) in the direction of the driveshaft (23).