PURPOSE: To improve copying precision in a copying method to copy the edge of a graphic previously read, especially the corner with a great curvature.

CONSTITUTION: A graphic 1 is photographed by a camera 2 in which photoelectric transfer elements are arranged, to convert signals from picture elements into binary data in a binary circuit to memorize in a binary data memory 12. A reference point 0 is set up and plural scanning lines A, B different in radius are also set up. A computation section 15 computes coordinate data for picture elements corresponding to the scanning lines A, B and a detection section 16 detects binary data for picture elements corresponding to the coordinate data and detects picture elements equivalent to the edge of the graphics 1. A judgement section 17 computes a vector between the detected picture elements and the reference point O, computes a mutual vector angle and issues a speed signal corresponding to the vector angle to drive a moving means.