To prevent cracking failure of a roll due to detection miss of a defect.

At the time of flaw detection after grinding a metal plate rolling roll, prestored past flaw detection results after grinding are compared with current flaw detection results after grinding. If the positions of defects are close to each other within a specified range, a decision is made that a defect is present at an identical part after current grinding and past grinding and then a decision is made whether that roll is used in next time rolling or not.