PURPOSE: To highly precisely control a sheet thickness by providing a calculating function to predict a rolling reaction force of a sheet to be rolled, a function to calculate a suitable initial interval of cross head corresponding to this predicted rolling reaction force and a mechanism to regulate the initial interval of the cross head to hold chocks.

CONSTITUTION: In a rolling mill having a cross head to hold working rolls and chocks of reinforcing rolls in the housing window of the rolling mill, a calculating function to predict a rolling reaction force of a sheet to be rolled, a function to calculate a suitable initial interval of the cross head corresponding to this predicted rolling reaction force, and a mechanism to regulate the initial interval of the cross head to hold the chocks are provided. Further, the hysteresis of an automatic sheet pressure controlling device (AGC) is always made small by setting into a suitable initial interval of the cross head corresponding to this predicted reaction force, the sheet thickness can be highly precisely controlled. Then, the hysteresis ton number is reduced, the error of the rolling reaction force detected value is made small, and the quality competitive power is improved.