An automatic contour tracking method for CAD in which a start element is indicated from continuous elements of a drawing on a display, and the tracking direction and the internal turn and the external turn are set, and the continuous elements are sequentially discriminated and selected according to the tracking direction and the internal turn and the external turn on the basis of the start element as the basic point whereby the contour data is obtained automatically, the automatic contour tracking method including finding an angle .theta. between a final selection element and a candidate element to be chosen next when the next candidate element to be chosen next appears on the final selection element, and selecting one element from among a plurality of candidate elements to be chosen by giving a priority on the element having a smaller angle .theta. in case the contour tracking is the internal turn, and giving a priority on the element having a larger angle .theta. in case the contour tracking is the external turn.

A polishing apparatus for polishing optical components and mechanical parts requiring a high surface precision, such as lenses and mirrors, by pressing a running tape to such component.