The invention relates to an apparatus for fiftering a suspension or emulsion and comprising a bed (6, 7) of a particulate filter material arranged in a container or tank (1). one or more inleta (8) arranged at the lower part of the bed for the suspenaion or emulsion to be filtered. means (3) for removing filtrate and arranged above the bed, elevator means (13) for conveying contaminated fitter medium from the lower part of the bed to a means (14) for washing or other treatment of the filter medium, and means for recycling treated fitter medium to the upper part of the bed. According to the invention, the elevator means (13) for conveying contaminated filter medium is arranged movable along the horizontal extent of the filter bed and is preferably placed on a carrier means (14) which can be given a reciprocating movemeret, is arranged above the filter bed and also carries the means (14) for treating the filter medium.