1. An apparatus for providing assistance in detecting mistranslation in a translated document obtained by performing machine translation of an original document, the apparatus comprising: a first acquisition unit operable to obtain a word included in the translated document; a second acquisition unit operable to obtain search results of searching both a first document data group and a second document data group including the first document data group for pieces of document data related to the word obtained by the first acquisition unit; a generation unit operable to generate, on the basis of the search results obtained by the second acquisition unit, an index indicating adequacy of the word obtained by the first acquisition unit as a translated word in a field corresponding to the first document data group; and an output unit operable to output the index generated by the generation unit.