PURPOSE: To provide a Japanese language input device capable of performing KANA(Japanese syllabary)/KANJI(Chinese character) conversion smoothly with correct reading when it is desired to acquire the same KANJI by acquiring the reading of KANJI notation in the Japanese language input device.

CONSTITUTION: The conjugation pattern of reading is stored in a conjugation pattern storage part 6. A new reading candidate is prepared by both a reading character string obtained by a reading acquisition part 2 and the conjugation pattern. Furthermore, a word with the same notation is selected from among a reading candidate by referring to a word dictionary 8. Thereby, the KANA/ KANJI conversion can be performed smoothly with the correct reading when it is desired to again acquire the same KANJI by acquiring the reading.