An abrasive grain-milling unit and a friction grain-milling unit are located on upper and lower portions of a pedestal, respectively. The friction grain-milling unit includes a grain feed trough to which a milled grain discharge trough of the abrasive grain milling unit is connected. A two-way grain feed trough and change-over valve is located above the abrasive grain-milling unit and is capable of selectively feeding grains either directly to the friction grain-milling unit or to the friction grain-milling unit via the abrasive grain-milling unit.