A content sharing system and a content sharing method of sharing contents following a free will of a user through belonging to a plurality of groups are disclosed. Identification information on each of one or more groups to which respective users belong is stored while associating it with identification information on the users. A download history of a content via user terminals by respective users is stored while associating it with the identification information on the users. A group or groups to which a user accessing via a user terminal belongs is/are determined. Whether a content already primarily downloaded by another user belonging to the determined group(s) exists is determined based on the download history and identification information. If the content already primarily downloaded by the another user exists, secondary download to the user terminal accessing the above-mentioned content is permitted.