Provided is a management system for managing a plurality of management target information processing apparatuses including a plurality of network apparatuses and a computer. This management system determines the reachability of a route network apparatus as a network apparatus on a communication between the system and the computer, and calculates a certainty factor concerning the certainty on whether a prescribed network apparatus contained in a route network apparatus based on the reachability is the cause of unreachability from the management system to the computer. The management system subsequently displays information showing that communication from the management system to the computer is unreachable, and the certainty factor as the certainty that the prescribed route network apparatus is the cause of unreachability.