1. A color image forming apparatus comprising: an image paper sheet for compensation including a testing image generated from an original image for testing, the testing image including a line image; a line width extracting means for reading color-by-color for a plurality of colors line widths of the testing image from the image paper sheet for compensation and extracting information of a state of toner scattering around edge portions of the line image; calculating means for calculating color-by-color correcting data based on the color-by-color extracted information; and line width cor recting means for correcting the toner scattering based on a result calculated by said calculating means for subsequent image forming operations.