In the present network system, a printer 10 periodically transmits an update request at different timings respectively to an apparatus management PC 30 and to a directory service 50 which are monitoring apparatuses for monitoring network apparatuses (such as the printer 10). Each of the monitoring apparatuses 30, 50 determines a state of the printer 10 based on the update request from the printer 10. Especially in the present system, if the apparatus management PC 30 determines that the update request from the printer 10 is not received, it notifies the directory service 50 by transmitting a delete request. As a result, early detection of disconnection of the printer 10 by the directory service 50 is possible without causing substantial increase in the network traffic.