To eliminate the fluctuation of reflection and to prevent the generation of a defective shape of a rolled material by controlling the acting force in the horizontal direction acted to the chock in a work roll to the positive value of a prescribed value or below while taking the rolling outlet side direction as the positive.

To a control flow applied at the time of stationally rolling, a judging means to judge whether the reacting force Fh in the horizontal direction is the positive value or not, is arranged. In the case that the Fh is zero or negative value, an offset quantity is again adjusted with an adjusting means for offset quantity Hs, and the reacting force Fh in the horizontal direction is recalculated based on this offset quantity. In such a way, the reacting force Fh in the horizontal direction is controlled so as to always become the positive value of a prescribed quantity or below. Then, the prescribed quantity is the quantity varied with various factors of a line specification in the rolling line, roll diameter, roll width, rolling speed, etc., and the suitable value is adopted from the operational result, etc. Therefore, the deflecting direction of the work roll can be kept constant all the time and the generation of a defective shape of the rolled material caused by the reversal of the deflection, can be prevented.