In an image processing apparatus which has an operating system (102) and scanner driver (103), is connected to a scanner (104) for reading an original and converting it into an image signal, and stores image data read by manipulating the scanner (104), a forgery determination processing module (103-2) of the scanner driver (103) compares the read digital watermark data with specific image data to determine the matching degree, and an anti-forgery control module (106) controls predetermined image processing on the basis of the determination result for the image data read by the scanner driver (103).