Since, for detecting a two-dimension code added to a document, the detection processing is performed by checking the four corners of the read image, if the user specifies an A3 size as a reading size of an image in the copy of an A4-size document, the two-dimensional code is not detected. When the document size detected by the copying machine differs from the reading size of the image specified by the user, the processing for the two-dimensional code detection is performed checking the four corners of the region of the document size detected by the copying machine.