PURPOSE: To improve cutting accuracy of a crop shear used for a hot rolling line, by using a corrective roll diameter to chase the rear end part of a rolled material and compensating wear and expansion of its measuring roll.

CONSTITUTION: A roll diameter of outlet side measuring rolls 4 is corrected, on the basis of the corrected roll diameter, control of cutting can be executed. That is, at cutting of the point end part of a rolled material, an inlet side measuring roll 3 is forcibly held to the rolled material by a lifting device 7, under this condition, a moving position of the point end of the rolled material is chased by using a pulse generator 3A and the detecting result of a rolled material detector 5 through a cutting controller 6 to detect a point of cutting time of the point end of the rolled material by a crop shear 2, on the basis of this detected signal, the shear 2 is driven and controlled. By this method, cutting accuracy of the crop shear can be improved.