A granular bed filter device comprising two gas-permeable walls bounding an annular filter bed disposed in a housing. The walls extend downwardly in a taper together and are inclined upwardly toward the central axis of the filter bed. A nozzle tube projects from above into the housing and has nozzles which are directed against the inner wall of the filter bed. In order to regenerate the dust-laden filter bed, compressed air is blown intermittently through the nozzle tube while at the same time the nozzle tube is set in motion by a motor. The accumulations of dust contained in the filter bed are ejected in agglomerated form through the outer wall and fall down into the region of a discharging conveyor.