The structure of entered document image data is analyzed and a character string in a text block that has been analyzed is subjected to pattern recognition. Synonyms and equivalents of words obtained as results of language analysis are extracted and words obtained as results of language analysis are converted to words of another language. A character string in a text block that has been analyzed is translated to another language. At least results of analyzing the structure of document image data, results of character recognition and results of language analysis are stored, and at least one of the results of extraction, results of conversion and results of translation are stored in a RAM in association with the results of character recognition.