Abstract: The instant invention relates to an improved filtering device adapted to eliminate any risk of clogging of the filtering material. The invention provides a filtering device for treating any effluents, which comprises a plurality of filtering walls arranged successively between a chamber containing the effluent to be filtered and a chamber containing the filtered effluent, each filtering wall being constituted by spacedly justaposed strips having a trapezoidal section with the large base of the trapezoid located on the inlet face of the filtering wall, said strips being separated from each other, on the inlet face of the filtering wall, by intervals of equal widths forming slots which define effluent inlet areas, the sum of said inlet areas constituting the total inlet area of a filtering wall, and the total inlet area of the upstream wall being less than the total inlet area of the adjacent downstream wall.