In a client processing apparatus, each application program independently performs communication with a server processing apparatus in spite of relevance between the application programs. For example, when plural application programs issue a request at the same timing in correspondence with a user's operation, the operation speed of the application program may become low. A request which occurs at the same timing of a particular request outputted from an application program to the server processing apparatus is previously defined in a communication grouping table. When the application program actually outputs a request, the communication grouping table is referred to, then the request and a request in the table to occur at the same timing are transmitted at once to the server processing apparatus. The server processing apparatus processes the plural requests at once, and returns the result of processing to the client processing apparatus.