To prevent generation of warp of a plate by adjusting the pressing force of a grinding wheel in association with the finish thickness of a rolled stock to keep the grinding capacity of a work roll constant in the maintenance of the grinding of the work roll.

While a rolled stock P is rolled by work rolls 1, 2, a hydraulic cylinder 8 is operated as necessary, a roll grinding device 5 is projected and a grinding wheel 3 is pressed against a roll surface to grind the surface of the rolls. When the finish thickness of the rolled stock P is changed, the position of a lower work roll 2 is fixed, and the height of an upper work roll 1 is adjusted. The pressing reaction in the tangential direction of the roll received when the grinding wheel 3 is pressed against the roll is measured by a strain gage 12. The value is inputted to a pressing force arithmetic unit 14 and operated, and the stroke of the hydraulic cylinder 8 is adjusted through a pressure control valve 13. The pressing component to the roll center can be kept constant, and the upper and lower work rolls 1, 2 can be uniformly ground.