It is provided a content recommendation system comprising a unit of storing the related information of the content; a history with respect to the content; determination information indicating whether to validate processing of extracting the recommendation content, which uses the each piece of the related information; and an effective period from a last use date, in which the determination information indicates valid; a unit of extracting the last use date of the each piece of the related information from the operation history, and, the determination information of the each piece of the related information to indicate invalid if a number of days elapsed since the last use date exceeds the effective period; and a unit of extracting the recommendation content by using at least one of the each piece of the related information of the content having the determination information thereof set to indicate valid and the operation history.