PURPOSE: To reduce the error of a sheet thickness and to reduce the off-gage by using a set-up value at a stable part in a section from the tip part of a material to be rolled to a designed calculation position as the reference value and executing correction to the temp. distribution in the longitudinal direction of the material to be rolled at the position of rolled length in each stand.

CONSTITUTION: The temps. of the material S to be rolled at inlet sides of the rolling mills HT1-HT3 are continuously measured, and calculation of the rolling mill according to the roll schedule is executed at the stable part of the tension and the load in the outlet side of each rolling mill. At the same time, the correction quantity of a roll gap to compensate the predicted load variation from the temp. difference between each part from the tip part at the outlet side of the rolling mill to the stable part is calculated. At the time of passing the material S to be rolled, the gap adding the correcting quantity at each position to the designed calculation value in the interval from the tip part to the stable part is controlled and after this part, the gap control is executed by an automatic sheet thickness control.