PURPOSE: To prevent the generation of ununiform roll wear by controlling the injection position of rolling oil to the surface of a rolling roll corresponding to the state of roll wear and the width of steel plate to be next rolled.

CONSTITUTION: The wear profile of the rolling roll 1 is measured at every ends of rolling with a profile measuring device 2 and the width of that worn region is inputted in an arithmetic unit 4 for oil applying position. The injection position of rolling oil is calculated with the arithmetic unit 4 for oil applying position so as not to produce difference of the surface level of the worn roll profile before and after the rolling of the stock to be next rolled by inputting the width of the stock to be next rolled from a width setting device 3. Closing command is outputted with a control device 5 for rolling oil injection nozzle to nozzles among injection nozzles 6 for rolling oil, which are situated in the position where rolling oil isn't made to inject according to the command for rolling oil injection position from the arithmetic unit 4 for oil applying position. In this way, the total injection quantity of rolling oil also is controlled, because the oil quantity per nozzle is fixed.