The present invention provides a roll mill to be used for a milling-dispersing treatment of a substance such as fine powder or nano particles in a material to be treated in production steps of various products such as ink, paint, ceramics, medicines, foods and electronic materials, wherein the roll mill has a full automatic electronic control by which the distance between rolls can be automatically controlled. The roll mill has, on a frame, center roll 1, and front roll 2 and rear roll 3 which are slightly movable in a perpendicular direction to the center roll by a servomotor and a ball screw. Between the center roll and the front roll and between the center roll and the rear roll, laser sensor 18 for measuring the distance between the rolls is disposed and load sensor 10 for measuring a pressing force between the rolls is disposed. An electronic automatic control mechanism is disposed which manages a constant distance and a constant pressing force by feed back of detected signals from each sensor, and which adjust the position of transfer rolls by driving the servomotor.