To allow a user to flexibly cope with to the fluctuations in communication traffic of a customer, which the user possesses and to allow a carrier to effectively utilize carrier's communication band.

A communication zone of a specified capacity is allocated to each user, in accordance with the utilization conditions set to each user. The utilization conditions include, for example, the route, maximum usage capacity, usage ratio, and use period. The users mutually adjust for excess and deficiency of use condition. A broker is provided with an information center, which receives request for reduction or expansion of the use condition from the users. It sets, in case of reduction request, a suggested sales price for transferring a surplus resource to other user, while in the case of expansion request, sets a suggested purchase price to take over a resource which is insufficient for expansion from other users. By presenting these to the users, for the users to mutually adjust the utilization conditions are adjusted among the users.