A system for tracing contour to prepare contour coordinates by tracing contour lines of a figure from an image that consists of a set of a plurality of lines, comprising a memory stored in advance from a basic pattern related to figure contour lines of positions of image transistion points between the neighboring two lines. An image transition point of a line is detected and another image transition point of a line that precedes the above line is detected, too. A pattern of image transistion points of the above two lines is extracted based upon the basic pattern. The thus extracted basic patterns are then integrated and are converted into contour coordinates.