Provided is a control computer coupled to a storage apparatus for storing a plurality of information resources and a search computer for receiving a search request containing a search condition and transmitting information resource list information containing at least one piece of information regarding an information resource corresponding to the search condition as a search result, the control computer includes a cache memory for storing at least one of the plurality of information resources, in which the control computer is configured to: receive the information resource list information from the search computer; calculate cache priority for each of the information resources based on the received information resource list information; decide at least one information resource to be stored in the cache memory based on the calculated cache priority; and store the decided at least one information resource in the cache memory.