PURPOSE: To manufacture a rolled metal plate excellent in metal plate accuracy by a rolling mill.

CONSTITUTION: The openings of a water control valve Vw and a lubricant valve Vc to control the flow rate of pure water W and lubricant O are controlled by a load deviation between a measured value of a rolled load from a rolled load meter L arranged on the upper part of a rolling mill A and a predicted value of a rolled load obtained by calculation of a process controller 2. The rolling oil made of pure water and lubricant and controlled in concentration is supplied between rolling rolls R,R and a material Po to be rolled to control a frictional coeffient between the rolling rolls R,R and the material Po to be rolled and the rolling load can be changed. In this way, the measured value of the rolled load can be approached gradually to the predicted value of the rolled load and matched to it, therefore, a rolled metal plate P1 excellent in thickness accuracy can be manufactured.