An image forming apparatus includes an external storage device insertion detecting section that detects that an external storage device is inserted. The image forming apparatus further includes an identification information generating section that generates identification information to identify the corresponding image information from the image information generated page by page by an image information generating section; an identification information comparing section that acquires previous identification information, which is previously generated by the identification information generating section, and that compares the acquired previous identification information with the identification information generated by the identification information generating section; and a printing executing section that executes a printing process for the image information corresponding to the generated identification information if a result of the comparison by the identification information comparing section indicates that the generated identification information does not match the previous identification information.