PURPOSE: To improve the efficiency of input operation by providing a means which stores an input KANA (Japanese character) storing and its converted result and retrieves them through simple operation.

CONSTITUTION: When document data is inputted by using a KANA-KANJI (Chinese character) conversion part 1 and a dictionary 2 for KANJI conversion, the KANA string of the document data and its conversion result are stored in a storage part 3. A display part 6 displays the converted result, and an operator when inputting a homonym recognizes that the word is already inputted. An input part 5 has a means which discriminates whether the inputted KANA string is a part of indexes of words and phrases or all indexes, and the operator decides on whether the KANJI conversion part 1 or a retrieval part 4 is accessed by the inputted KANA string. The retrieval part 4 uses input retrieval information as a key to search the storage part 3. Consequently, words and phrases which are used once are inputted easily, so the efficiency of input operation is improved.