To extend the service life of a roll die by reducing the load to a roll die and to reduce the energy consumption of rolling work by finding out an appropriate rolling pattern to a workpiece.

Roll die forcing devices 17, 18 are forced in at high speed after coming into soft contact with the workpiece 28 when rolling the workpiece 28 to be worked by the screw point of the roll dies 7, 8 and, by performing the drive control of the roll die forcing devices 17, 18 so that the rotational torque of the roll dies 7, 8 to the workpiece 28 to be worked when rolling the intermediate portion of a crew thread of the roll dies 7, 8 become a prescribed maximum value and, when rolling the thread of the rolling dies 7, 8 to the workpiece 28 to be worked after that, the rolling is performed at the lowered prescribed rotational torques of the roll dies 7, 8.