PURPOSE: To prevent the disorder of flatness of a thick plate, by rolling the plate till an edging pass by a target-thickness system, and then rolling it in a thickness controlling pass by a target-load system after performing the 2nd scheduling calculation taking in an error of loading model.

CONSTITUTION: In a thick plate rolling, the plate is rolled till the passes of forming and edging by a target-thickness system for the purpose of securing the accuracy of the plate breadth. In a thickness controlling pass after finishing the edging, the 2nd scheduling calculation is performed basing on a loading model, obtained by using a cumulative value of the ratio between an actual load and a calculated value, for the purpose of correcting an error of load estimation, thereby the accuracy of load estimation at the time of the scheduling calculation is improved. Then the rolling system is changed to the target-load system after performing the 2nd scheduling calculation, thereby the disorder of flatness is prevented.