1. A user activity estimation system which estimates a user activity from an article to which an article identifier for identification of an article is attached, comprising: attribute information holding means for holding the article identifier associated with article information; probability information holding means for holding a relationship between a noun relating to the article information and a verb relating to the article associated with a conditional probability; and activity estimation means for estimating a user activity upon detection of the article identifier based on contents held in the probability information holding means.