To assist dealings in commodities and to carry out effective advertisement.

An article presenting part 35 presents articles to users via a network. A sponsor presentation part 36 presents sponsors which adds advertisements to the articles, while associating them with the articles. A discount presentation part 38 presents an amount that a sponsor bears instead of a user, when the user acknowledges the addition of advertisement by the sponsor. When the user purchases an article, a purchase reception part 42 inquires whether the user acknowledges the addition of the advertisement by the sponsor to the article.