1. A machine translation apparatus including a plurality of target language document databases used for a translation from an original language to a target language, comprising: a database control unit configured to assign a priority degree to each of the plurality of target language document databases, and to indicate which of the target language document databases has the highest priority degree; a translation word generation unit configured to generate a plurality of translation word candidates of an original word for the translation; and a translation word learning unit configured to select a translation word as the translation from the plurality of translation word candidates by using the target language document database indicated by said database control unit.