PURPOSE: To improve the precision of the thickness of a rolled sheet, sheet crown and shape by learning/calculating the distribution in the axial direction of roll of variation of roll radius using a calculation model of thermal expansion of roll and the calculating model of roll wear.

CONSTITUTION: The distribution in the axial direction of roll of roll radius in rolling operation using a polynomial is calculated by the calculation models of the distribution Ut (z) of thermal expansion and distribution Uw(z) of roll wear in the axial direction of roll. Further, using the measured value of work roll profile in rolling operation, the distribution Up (z) in the axial direction of roll of the change of roll radius from the initial value is calculated and the distribution A(z) in the axial direction of roll of the learning factor by which Up (z)=A(z). Ut(z)+Uw(z) is satisfied is determined. When the estimated value of the calculating model of Ut (z) is over a preset value, by correcting the distribution in the axial direction of the variation of the radius of work roll as ΔR(z)=A(z). Ut(z),/)-' +Uw(z), the precision of the thickness, sheet crown, etc., is improved.