PURPOSE: To better initial windability of a steel plate automatically by comparing the rotation speed of an electric motor for driving a winder and the target speed and using the output as a correcting input signal to a voltage controller.

CONSTITUTION: A rotation speed detection signal of the DC electric motor 7 for driving the winder given from a rotation speed meter 10 is given as an input signal to a relational operator 11. The target speed determined by thickness of the steel plate, i.e. a setting signal of lead ratio, is given to another input side. The rotation speed detection signal is differentiated by a rotation speed differentiator 12, and maximum value of overshoot is detected to operate the relational operator 11. The rotation speed detection signal and target speed setting signal are compared by the relational operator 11 and the operational output is used as a correcting input signal to the voltage controller 1. Thus, rotation speed of the electric motor 7 is controlled, and then switched over to tension control.