The present invention provides a content-on-demand system capable of managing users' system-utilization frequencies such as download counts and connection times as well as changing the quality of a content transmitted from a server to a user in dependence on the system-utilization frequency of the user. Thus, a high-quality content or a highly functional content is provided to a user with a high system-utilization frequency. By differentiating contents provided to users in accordance with the system-utilization frequencies of the users, network businesses can be activated.