1. A machine translation apparatus comprising: a document receiving unit configured to receive an input of a source language document described in a source language; a first translating unit configured to translate the source language document into a translated document described in a target language in a first translation process, and to identify a document ambiguous portion that is a word or a sentence, for which a plurality of candidate translations occurs during the first translation process; a storing unit configured to store the translated document and the document ambiguous portion; a speech receiving unit configured to receive a speech in the source language; a recognition unit configured to recognize the speech received by the speech receiving unit and to create text of a source language speech sentence as a recognition result; a second translating unit configured to translate the text of the source language speech sentence into the target language; an extracting unit configured to extract a source language document sentence relating to the source language speech sentence from the source language document; an updating unit configured to: select, when the extracted source language document sentence includes the document ambiguous portion, a translated portion of the source language speech sentence corresponding to the document ambiguous portion of the extracted source language document sentence, the translated portion of the source language speech sentence being obtained by a type of ambiguity identification that is the same type of ambiguity identification as was used in the first translation process that identified the document ambiguous portion; retranslate the source language document using the selected translated portion of the source language speech sentence, and the extracted source language document sentence relating to the source language speech sentence; and update the translated document stored in the storing unit using the retranslated source language document; and a display control unit configured to display the updated translated document on a display unit.