PURPOSE: To make the drawing up of highly accurate numerical control data attainable, by performing a specific operation process in case of making a copying profile using a rotary matrix into the promotion of numerical information, in copying metalcutting technology in machine tools.

CONSTITUTION: A copying attachment 10 to be used for operation of a copying numerical information promoting method is provided with a stationary column 12 and fitted with a tracer head 16 having a stylus 18 in its tracer support 14. Next, when numerical information for numerical control is drawn up with each detected value out of X-, Z- and A-axes by a copying controller 28, as these detected values out of said X-, Z- and A-axes, values detecting such a point that a difference between an interpolating straight line between two points in a three- dimensional space and a curve along an actual curved surface reaches an incremental method are used. With this method, highly accurate numerical control data is made possible to be drawn up.