PROBLEM TO BE SOLVED: To present a plurality of documents similar to each other more in accordance with taste of a user than in the conventional manner.SOLUTION: A difference between a plurality of documents having a mutual similarity to each other is extracted. It is discriminated whether the difference represents that an interest keyword representing an item interesting to a user satisfies a prescribed condition, the interest keyword being previously stored in interest keyword storage means. If the difference represents that the interest keyword satisfies the prescribed condition, the whole existence of the plurality of documents are presented, and in other cases, the existence of a portion (for example, a document called "AAAAA1") of the plurality of documents is presented preferentially.
