1. A content recommendation system comprising: attribute value storage means for storing an attribute value of each of one or a plurality of attributes for each of a plurality of contents; preference distribution storage means for storing a degree of user's preference with respect to each attribute value for each of the attributes; attribute value acquisition means for obtaining an attribute value of at least one attribute for each of one or more contents owned by a user; preference distribution update means for updating a content stored in the preference distribution storage means, based on the attribute value obtained by the attribute value acquisition means; condition determining means for selecting attribute values of one or more attributes according to a probability based on the degree of user's preference stored in the preference distribution storage means, and determining a condition for the attribute values of one or more attributes according to the selected attribute value; content selection means for selecting some or all of the plurality of contents according to the condition determined by the condition determining means; and content presenting means for presenting the contents selected by the content selection means to the user.