To reduce the data volume of a document picture and to hold document data in such a form that data can be easily used again.

A multi-valued picture original 101 is optically read to obtain original image data. Character areas 106 to 108 and image areas 102 to 105 are extracted from obtained original image data, and respective position information are acquired. Image data in character areas are subjected to character recognition, and recognition results are stored in a text layer 116. Image data in image areas are subjected to compression processing, and processing results are stored in a picture layer 112. Data obtained by compressing the whole of original image data are stored in an overall picture layer 111.