Disclosed is an arrangement of a filtering element for a device for purifying gas from the crankcase of an internal combustion engine, which includes: a filtering element mounted so as to rotate about an axis and having an annular filtering medium; a rotor element capable of being part of a rotating system, making it possible to turn the filtering element by way of notches formed on the outer surface of a sleeve. The flanges of the filtering element are attached to one another in an inner space defined by the medium, typically by snap-fitting, using at least one retaining member and an anchor portion engaging with one another with an anti-rotation effect. The anchoring portion is provided with inner projections forming contact surfaces, preferably angular, which are inserted into the notches of the sleeve when the rotor element is inserted into the inner space.