A roll mill for a milling-dispersing treatment has a fixed roll fixed to a frame, and a transfer roll displaceable into and out of contact with the fixed roll in a direction perpendicular to the fixed roll by a servomotor and a ball screw. A laser sensor disposed between the fixed roll and the transfer roll measures the distance between the rolls, and a load sensor measures a pressing force between the rolls. An electronic automatic control device maintains a constant distance and a constant pressing force between the fixed roll and the transfer roll by feedback of detection signals sent from the respective sensors, wherein the servomotor is driven by the electronic automatic control device to adjust the position of the transfer roll.