PURPOSE: To roll flat thin steel plate by uniforming the widthwise tensional distribution of plate by the procedure in which a fixed crown is given to any one of fixed roller or movable roller at least and the movable roller is transferred controllably to an appropriate position in correspondence with the coil diameter of winder.

CONSTITUTION: When a fixed crown is given to each of the fixed roller 16 and the movable roller 17, and the widthwise tensional distribution of rolled material 18 is made uniform, the relation between the end elongation rate corresponding to the various coil diameter 14 of the wound coil 13 and the turning angle α of the movable roller 17 can be obtained from the known equation, and when the turning angle α of the movable roller 17, at which the end elongation rate becomes zero, is obtained for every coil diameter 14, the curve 22 is obtained. From the curve 22, the coil diameter 14 is measured by a proper means during rolling, the turning angle α of the movable roller 17, corresponding to the measured value, is determined, and the movable roller 17 is transferred controllably to the positin α, thus uniforming the widthwise tensional distribution of plate.