A control station communicates with at least one base station in a wireless network system. The control station includes a storage and a controller. The storage stores reference data for calculating the idle time according to the number of terminals. When an arbitrary one of the base stations undergoes a change in the number of terminals, the controller sets an idle time calculated by the reference data stored in the storage as the idle time of the base station using the changed number of terminals. As a result, the control station resets the idle time of each base station according to the number of terminals communicating with the base station, so that the base station can be relieved of a load of wireless resources, and smoothly accommodate terminals more than before.