Abstract: Print image data produced by external equipment such as a personal computer is temporarily stored in a page buffer of an IOCP. The print image data stored in the page buffer is divided into a plurality of parts so that each divisional part can be transferred to another page buffer of a main control circuit within a scan return period of a scanner. Image data to be transferred to the page buffer of the main control circuit is selected by a multiplexer between the print image data and copy image data from the scanner. Thus, the print image data and copy image data is processed by an image processing system in a parallel manner.