PURPOSE: To provide a true rolling load by measuring the strain of a column supporting the rolling load, and correcting the strain of the column by a temperature change.

CONSTITUTION: A rolled material is inserted between upper and lower work rolls 6, 6, a pressing screw 4 is rotated, an upper housing 5 is vertically moved to adjust the interval between the rolls 6, 6, and a prescribed rolling load is applied to the rolled material. The load is supported by four columns 3, the columns 3 are extended in the axial direction, and the extension is measured by a strain gauge 14 as the strain against a guide rod 12. The temperature of a rolling machine 1 is increased with rolling, and the columns 3 are also extended by it. The total strain is measured by the strain gauge 14, and it is inputted to an apparent load calculating means 18 to obtain the apparent rolling load. The measured results of the inner and outer thermometers 15, 16 of the columns 3 are inputted to a temperature strain calculating means 19 to obtain the temperature strain of the columns 3, and it is inputted to a temperature drift load calculating means 20 to obtain the temperature drift load. The outputs of the means 18 and the means 20 are inputted to a true load calculating means 21 to obtain the true rolling load.