A web site determination unit determines web sites associated with any one of a plurality of users of interest. A web site association unit associates, among the determined web sites, a plurality of the web sites with each other, each of the plurality of the web sites satisfying at least one of a condition on a feature amount of the each of the plurality of the web sites and a condition on at least one of the users of interest associated with the each of the plurality of the web sites. Accordingly, web site groups possibly having a commonality may be determined among web site groups associated with users of interest.