The management server includes an overload detecting unit that detects whether or not the management server is overloaded, a priority deciding unit that, if the management server is overloaded, searches the image forming apparatus database for the serial number in the processing request received by the request receiving unit, obtains the information of the image forming apparatus that sends the processing request, and decides a priority of processing the processing request on a basis of the obtained information, a request processing unit that processes the processing request, the priority deciding unit having decided that the processing request has a high priority, and a delay-request requiring unit that sends a delay-request requirement to the image forming apparatus that sent the processing request, the priority deciding unit having decided that the processing request has a low priority, the delay-request requirement requiring to resend the processing request after a specified time.