PURPOSE: To obtain a titled device of a rolling mill for accurately holding the thickness of a material to be rolled in the target thickness, by calculating the deviation of the sheet thickness at the position existing just below the rolling stand, and constituting the device which controls the sheet thickness so as to make the deviation to zero without causing any time lag.

CONSTITUTION: Respective outputted signals of a load meter 9 and a rotational speed detector 8 are inputted to a load difference operating device 10, which follows up a material 1 to be rolled by an outputted signal of the detector 8 to calculate a rolling load P0 acting on a part of the material 1 existing just below a thickness gauge 4 at present, at the time when said part was situated just below a rolling stand 2. Then the difference between a rolling load P1 at present and said P0 is obtained, and a signal (P1-P0) is outputted. Output signals of a position detector 5 and a detector 8 are inputted to a reduction moving quantity operating device 11, which calculates in the same manner as the device 10, the difference between a roll gap S0 of the stand 2 detected at the time when the part of the material 1 existing just below the thickness gauge 4 at present, was situated just below the stand 2 and a roll gap S1 of the stand 2 at present, and outputs the difference (S1-S0). That is, the sheet thickness is controlled so as to make the deviation of the sheet thickness to zero after calculating the sheet thickness deviation at the position existing just below the stand 2.