A method for classifying a ground material-fluid mixture and a mill classifier improve the grinding and classification process, wherein a fine material-fluid flow leaving a dynamic classifier part with angular momentum is subjected to a swirl reduction or swirl elimination, with the aid of a guiding apparatus and a displacement body and is made uniform in a classifier outlet housing and deflected into a virtually linear flow. The fixed guiding apparatus arranged coaxially with the classifier axis in the classifier outlet housing and the displacement body may be formed as one unit, and the guide elements of the guiding apparatus may be arranged on the displacement body and extending into the vicinity of the inner wall of the classifier outlet housing.