1. A method for tracing an object wherein the object is sensed by a set of sensing elements included in an optical head which moves along the object, to detect a position and a direction of the object, wherein the optical head is controlled to trace the object depending on the detected position and the direction of the object, and wherein the object is reproduced by reproduction means which is moved in synchronization with the optical head, the improvement comprising the step of moving the optical head along portions of the object, which the sensing elements can discriminate hardly or not at all nor follow the object, according to line segment data which are stored previously by coordinate reading means and may be predetermined and represent a plurality of points of coordinates.