A machine translation system including an input unit, a first text memory, a translation dictionary, a translation processor, a second text memory, and a control editor. The first and second text memories respectively store an original text and a translated text. The translation dictionary includes a word/idiom dictionary. The translation processor executes translation processing of the original text using the content of the translation dictionary to obtain the translated text. The control editor controls the respective units, and performs edit processing of at least the translated text. The control editor includes a changing section for changing a translated word in the translated text corresponding to a designated word in the original text to another translated word, and a replacing section for, when the translated word in the translated text corresponding to the designated word in the original text is changed to another translated word by the changing section, providing priority to a translated word in which a translated word portion corresponding to the designated word in the original text is replaced with the other translated word as a translated word corresponding to an entry word including the designated word in the original text in the word/idiom dictionary.