The invention relates to a device for size-reducing agglomerates and the like material to be reduced in size. The device comprises a rotatingly driven rotor (7) having a plurality of wing-type size-reduction tools that can be brought into contact with the material in order to cut it. The aim of the invention is to provide a device for size-reducing agglomerates and the like material and a corresponding method which allow better size-reduction results and prevent, in combination with additional methods, the material from baking on. For this purpose, the size-reduction tools are composed of narrow knives (24) the thickness thereof measured in the axial direction of the rotor does not exceed 20 mm and the spacing between the knives in the axial direction is not more than 50 mm.