To make easily retrievable a specific part of a document.

One set of sub-documents are set base on one set of documents (S102). A query acting one set of sub-documents as objects is processed, and a score is generated to each sub-document (S104). The score of each sub- document indicates relevance to the query of the corresponding sub-document. The score is examined (S106), and an optimal sub-document is retrieved (S108). The optimal sub-document has the score indicating the highest relevance to the query. The next optimal sub-document is retrieved based on the selection of a user. The sub-documents are shown to the user in the order of the scores. Also, a document including the sub-document with the optimal score is displayed, and automatically scrolled to the position of the sub-document. The document is automatically scrolled to the position of the next optimal sub-document based on the input of the user. When the next optimal sub-document is included in another document, the document is automatically loaded.