PURPOSE: To keep the inner surface of a raw material charging chute clean by providing shaking levers revolving in a radial direction to the rotary shaft provided in the raw material charging chute in a suspended state, and arranging the rakes connected to the shaking levers by pins at an almost equal interval in the axial direction of the rotary shaft over two or more stages.

CONSTITUTION: A plurality of freely rotatable grinding rollers 4 are arranged to the upper surface of the outer peripheral part of a turntable 3A, and the raw material supplied through the raw material charging chute 17 suspended directly above the central part of the turntable 3A is ground between the upper surface of the turntable 3A and the peripheral surfaces of the grinding rollers 4 by applying predetermined grinding pressure to the grinding rollers 4. A freely rotatable rotary shaft 110 is provided on the center axis from the part directly above the raw material charging chute 17 in a suspended state. Shaking levers 120 are connected to the rotary shaft 110 by pins so as to be revolved in a radial direction and rakes 130 are connected to said levers 120 by pins to be arranged at an almost equal interval in the axial direction of the rotary shaft over two or more stages. As a result, the adherend on the inner surface of the raw material charging chute can automatically be removed during operation by remote operation and the smooth supply of a raw material can be ensured.