The each AP includes a control unit that detects, as the wireless environment information, a signal detection level for one or more neighboring APs positioned in the neighborhood of the AP and notifies the detected signal detection level to the central coordinator, and controls the ATT value by the setting in the central coordinator; and the central coordinator includes a parameter calculation unit that calculates the ATT value for each the APs, based on the signal detection level for each the neighboring wireless access point notified from the plurality of APs and based on an RSSI threshold at which each the APs is able to secure a prescribed service area.