In a system in which multiple independent search servers are loosely coupled, a duplicate entry is detected and eliminated from search results sent from the respective search servers with respect to the same search condition. An integrated search control part of the search server, upon receiving an integrated search request, determines a hash algorithm to be used in common by the respective search servers. Each search control part responds to the integrated search control part by adding a hash value, based on this hash algorithm, to the search result. The integrated search control part detects and eliminates a duplicate entry on the basis of the hash value.