PURPOSE: To forestall any chatter being produced during grinding a mill roll by way of controlling the rotational frequency of a grinding wheel and an amount of infeed or feed rate.

CONSTITUTION: In an automatic grinding attachment 2 grinding the peripheral surface of a milling roll 1 as rotating this roll, it is provided with a sensor 7 detecting the vibro-amplitude value of a grinding wheel 3, and it is also provided with a control unit 8 controlling those of rotational frequency, infeed or feed rate in conformity with the vibro-amplitude value, the absolute value of this vibro-amplitude value, the.integrate value or the absolute value of this amplitude value and differential value at each specified time being inputted from the sensor 7, in a direction where the said vibro-amplitude values are lowered. With this constitution, occurrence of a surface defect in grinding operation is sharply reducible and simultaneously a span of grinding operation time can be shortened, and thus operation efficiency is well improvable.