PURPOSE: To hold the inner surface of a raw material charging chute in a clean state by concentrically connecting a short pipe whose diameter is smaller than that of the raw material charging chute to the upper end of the raw material charging chute and providing an elevatable annular cutter in the raw material charging chute.

CONSTITUTION: A short pipe 17b is connected to the upper end of a raw material charging chute 17 and a stepped part 17c is formed. An annular weight 110 and the annular cutter 120 connected thereto are received in the stepped part 17c and a wire 130 is guided by a pulley 140 to be connected to the electromotive winch 150 arranged on the outside of the casing of a vertical grinder. The weight 110 and cutter 120 within the raw material charging chute 17 can rise and fall in a vertical direction corresponding to the forward and reverse rotation of the electromotive winch 150. The cutter 120 is reciprocally moved along with the weight 110 along the inner surface of the raw material charging chute by the forward and reverse rotation of the electromotive winch 150 to make it possible to cut and detach the matter 50 adhering to the inner surface of the raw material charging chute 17.