A first interface accepts a user specified first question sentence. A question analysis unit analyzes the first question sentence. When the first question sentence queries a plurality of matters, the question analysis unit generates a plurality of second question sentences for individually querying each of the plurality of matters from the first question sentence. A search engine makes searches for documents which match respective matters queried by the plurality of second question sentences from a morphological index database in accordance with the plurality of second question sentences. A second interface provides a user with a search result for the first question having reflected thereon results of document searches for the plurality of second question sentences by the search engine.