An image forming apparatus that allows easy and reliable extraction of a hand-written image and allowing reliable execution of a desired process on image data based on the hand-written image is provided. For this purpose, during a mark adding process, a scanner unit and an image processing unit form YMCK data based on an original image; a specific area extracting unit extracts image data of a specific area from the YMCK data; a mark image adding unit combines image data of the specific area with the mark image data to form combined data; and a printer unit outputs a first image based on the combined data. During image processing of the specific area, the scanner unit forms RGB data based on the first image; the mark area extracting unit extracts image data of the mark area from the RGB data; the specific area image processing unit performs prescribed image processing on the image data of mark area; and the printer unit outputs a second image based on the YMCK data after the prescribed image processing.