PURPOSE: To prevent the vibration of a bearing case with which a driving shaft is supported, improve durability of a needle bearing and improve setting of the optimum balance load and workability.

CONSTITUTION: A driving roll 3 and a driving spindle 9 are connected through the driving shift 11 provided with splines 16, the driving shaft 11 is supported with the bearing case 18, the bearing case 18 is balanced with a pressing means 28 through pressurizing mechanisms 27 with which the bearing case is brought into contact with the sliding parts 30 of guide plates 19 and balance load is added by always pressing the bearing case 18 further toward the work rolls 1 with a hydraulic cylinder 32.