Abstract: A method of converting an area data, which is a rectangular or polygonal area data having an area, into a path data, which has both a series of central line segments and a width data. The area data is inputted into a computer where the area data is converted into the path data, based upon a connection relation among figures. The path data is then outputted by the computer. The method can also include the steps of determining whether or not the area data can be converted into one path data based upon whether or not the area data has an edge which fulfills a condition of the shape of the outline at corresponding corners, other than the first and last corners counted from one edge are the same, and when the corresponding corners are numbered from the one edge both clockwise and counterclockwise, all the rectangles whose opposite corners are the corresponding corners are included in the original figure.