Abstract: A hammer mill for batchwise operation has a mill housing having a perforated screening plate intended for discharging a fine fraction of the milling material. A coarse fraction of the milling material is emptied through an emptying flap. A supply shaft opens tangentially into the milling chamber. The supply shaft is closed by a movable closure wall. In order to maintain short consistent treatment times of the milling material and to precisely reproduce a specific degree of filling for the treatment space, the supply shaft is dimensioned such that it can receive more than a milling-chamber fill. The movable closure wall is displaceable back and forth between a raised standby position and a lowered operating position such that the milling material introduced into the supply shaft when the closure wall is raised is forced into the milling chamber and then held therein by the closure wall being displaced in the direction of the milling chamber.