PURPOSE: To automatically detect the surface flaw with high precision by installing a control means which carries out the eddy current testing for detecting the surface flaw and corrects the polishing quantity.

CONSTITUTION: A eddy current testing head 33 is brought into contact with the outer peripheral surface of a roll 1 for rolling by the instruction of a controller 5, and the eddy current testing is carried out by the outputs of the eddy current testing coils arranged between a plurality of contact rollers installed on the eddy current testing head 33. During the revolution drive of the roll 1 for rolling, the eddy current testing head 33 is relatively shifted in the axis line direction of the roll 1 for rolling. Accordingly, the surface flaw is detected in the wide range on the surface of the roll 1 for rolling, and the polishing quantity is corrected, and the surface flaw is removed. In this case, the relative shift of the eddy current testing head 33 in the axis line direction of the roll 1 for rolling is easily realized by installing the eddy current testing head 33 on a wheel spindle stock 18 on which a grinding wheel 19 is placed.