As a retrieval result, appropriate text of a second language is provided in response to a retrieval request by text of a first language. A first directory storing part stores a first directory structure created for a first language. A second directory storing part stores a second directory structure created for a second language. A directory relation storing part stores correspondences between directories in the first directory structure and directories in the second directory structure. A directory retrieval part receives a retrieval request by the first language from a user and decides which directory in the first directory structure the request has a high degree of relation with. A multilingual retrieval part decides documents having a high degree of relation with the retrieval request, of documents belonging to a directory in the second directory structure that corresponds to the decided directory.