PURPOSE: To reduce warping quantity of rolled material after rolling by reversing the relation between high and low of the peripheral speeds of the upper and lower rolls of a stand in the previous stage and the relation between high and low of the peripheral speeds of the upper and lower rolls of a stand in the adjacent following stage.

CONSTITUTION: In the No. n-1 stand the peripheral speed of the lower roll R(n-1)2 is set higher speed than the upper roll R(n-1)1. In the No. n stand, the upper roll Rn1 is higher than the peripheral speed of the lower roll Rn2, and in the No. n+1 stand, the peripheral speed of the lower roll R(n+1)2 is higher than the upper roll R(n+1)1. When it is assumed that rolling material S is subjected to rolling from the upper stream and then by the No. n-1 stand and has lost all its warping, in the next No. n stand, since the peripheral speed of the upper roll Rn1 is higher than the lower roll Rn2, after pinching, it becomes downward warping. After pinching of the next No. n+1 stand, it has upward warping to cancel the warping of the rolled material S.