A document image data storing and controlling system including a document image data storing unit for storing document image data as partial image data which are areas divided according to the attributes such as a text, a graphic, a table, etc.; and a document image data rewriting unit for reducing the amount of the document image data by deleting the partial image data whose degree of importance of information is low, or by lowering its resolution in the document image data. By employing this system, for example, in a portable storage device whose storage amount is limited, a storage amount for new data can be secured while leaving effective information of the document image data.