In a management system for managing network devices connected to a network, it is considered to reduce the load of the network and the devices by preserving device information acquired from each device and not acquiring new information from the device for a predetermined period. However, this approach has a problem in that the user cannot know when the displayed information was acquired. In the present invention, when preserving device information, the time of acquisition of the device information is preserved as acquisition-time data, which is displayed within displayed information together with the device information. The above-described probem is thereby solved, and the user can acquire very reliable information.