A color image forming apparatus of a so-called tandem type which has image forming units in correspondence with colors is provided. In the color image forming apparatus, a color discrepancy amount storage unit stores information of a color discrepancy amount of each of the image forming units, which is measured in advance. A first color discrepancy correcting unit performs color discrepancy correction in a pixel unit by performing coordinate conversion of bitmap data to be printed based on the information of the color discrepancy amount stored in the color discrepancy amount storage unit. A second color discrepancy correcting unit performs color discrepancy correction in less than a pixel unit by performing tone correction of the bitmap data corrected by the first color discrepancy correcting unit based on the information of the color discrepancy amount stored in the color discrepancy amount storage unit.