To improve the precision of a roll reduction position zero adjustment and a leveling zero adjustment by stopping the rotation of a work roll to reduce a thrusting force and reducing the dispersion of the difference load of the leveling zero adjustment.

The leveling zero adjustment is executed in the case of recombining the work roll. In this case, in order to prevent the thermal deformation of the work roll, the work roll is stopped to rotate after taking such an action as spraying a cooling water or the like. By this way, the thrusting force is reduced and the dispersion of the difference load of the leveling zero adjustment is reduced. That is, the dispersion of the leveling zero adjustment value at the time of the zero adjustment is small and conforms to the leveling zero adjustment value at the time of rolling by adjusting an objective difference load. By this way, this method is not influenced by the variation of the difference load caused by the thrusting force due to the cross angle between the rolls.