A network management system includes a plurality of terminal devices, and a network to which the plurality of terminal devices are connected. At least one of the plurality of terminal devices includes a management setting information changing system configured to change management setting information for managing network use by the plurality of terminal devices, and a management setting information restoring system configured to perform a restoring operation for restoring the management setting information changed by the management setting information changing system, in response to a predetermined restoring condition being satisfied. The present arrangement enables use of at least one peripheral device by the plurality of terminal devices according to different management settings.