PURPOSE: To automatically sort image information of a document by pages on the processor side and to register it substantially in the page order by providing an image information registering means which registers the image information of the document on a recording medium on the basis of page information which is rearranged in the page order.

CONSTITUTION: An OCR board 60 is connected to an interface circuit 36 and a page memory 40, and has a function for recognizing the characters of effective character string information of the document on the basis of stored data in a specific area of a page memory 40 temporarily storing the image information to be stored on an optical disk 19 and supplies the recognized effective character string information to a CPU 34 through the interface circuit 36. Then the CPU 36 sorts the pages of the document to be registered on the basis of the effective character string information. Namely, the pages can automatically be sorted by the page number reading function of the OCR board 60 and the document which is given pages at specific positions can automatically be registered in the page order when registered on the optical disk 19 by performing the page sorting processing on the processor side.