Processing time required from transmission of a request packet including a processing request from a client, until return of a reply packet in which internal information including an operation status of a plurality of servers is added to an execution result of processing corresponding to the processing request, obtained by the servers in cooperation with each other, is calculated by a function incorporated beforehand in the respective servers. Moreover, the internal information added to the reply packet is extracted and stored in an internal information DB in association with the calculated required time of the processing. Furthermore predetermined statistical processing is performed with respect to the internal information and the required time associated with the internal information stored in the internal information DB to analyze the operation status of the plurality of servers.