PURPOSE: To improve the efficiency of editing documents by providing a means which registers the name of the dictionary and the name of the field in a format data and refers to this.

CONSTITUTION: A format information file stored in a hard disk 6 is opened and loaded on a main memory 5. Then, the document file to be edited is opened. The document file is stored in the hard disk 6 and loaded on the main memory 5 when opening the file. In the conversion field flag of the format information, the bit which is used for the KANA (Japanese syllabary)/KANJI (Chinese character) conversion processing at the time of preparing the document, for example, in the medical field is turned ON. In preparing the document while performing the KANA/KANJI conversion, words in the conversion field (medical field) which is set to the conversion field flag in the format information is found in advance so as to make a conversion.