CPU of a sheet processing apparatus reads a sheet by a scanner, stores the image of the sheet in an image memory, checks to determine whether expanding, reducing, rotating, synthesizing or other editing operations have been performed for the sheet image stored in the image memory and performs processing for converting the image to a recognizable size and rotating an image before recognizing the read sheet image when determining that editing has been performed. CPU further recognizes sheet ID information contained in the sheet image stored in the image memory by means of a character recognizing section, selects an unrecorded sheet image corresponding to the sheet ID information from a hard disk, stores the image in the image memory and prints out by way of a printer. Thus, sheets synthesized, expanded/reduced, rotated or edited in other ways can be recognized and high image quality of clean and unrecorded sheets can always be provided, thereby maintaining a good recognition rate.