PURPOSE: To amplify the force of the device and to miniaturize and simplify the device by providing the roll bending device for moving the shaft box along the inclined surface of the inclined guide surface.

CONSTITUTION: On the case that the roll bending force PB is applied to the direction parallel with the wall surfaces 5a, 5b of the inclined guide component 5 with the roll bending device 9 on the rolling mill, the bending force PB can be decomposed into the force Py which passes through the center O1 of the intermediate roll 2 and is toward the center O2 of the upper back up roll 3, and the force Px which passes through the center O1 of the intermediate roll 2 and faces toward the orthogonal direction to the side surface 4a of the shaft box 4 and the wall surface 5a of the inclined guide component 5. If the ingredient of vertical direction of Py is made as F, F=cosα/cos (θ+α).PB is composed, and cosα/cos (θ+α)>1, so F>PB, and if the roll bending force PB is multiplied, the composition F of vertical direction is amplified.