PURPOSE: To optionally control the peripheral speed ratio of a rotary roll for correction and a grinding grindstone, by controlling a driving device so as to make the peripheral speed ratio under correction of the rotary roll for correction and a grindwheel settable in variable speed optionally at the correction grinding action point of the correction rotary roll and grindwheel.

CONSTITUTION: A feeding device 20 feeding a rotary roll 5 for correction with its carrying in about radial direction between the outer periphery and center part of the grindwheel 2 end face and the rotation driving device 26 of the grindwheel 2 and the rotation driving device 8 of the rotary roll 5 for correction are arranged, and this roll rotation driving device 8 is taken as a constant rotating speed driving device. Moreover the rotation driving device 26 of the grindwheel is made a variable speed driving device, or the rotation driving device of the rotary roll for correction and that of the grindwheel are made variable speed driving devices and the peripheral speed ratio under correction of the rotary roll for correction and the grindwheel is made variably settable optionally at the correction grinding action point of the correcting rotary roll and grindwheel by controlling the driving devices with control units 24, 25.