In network groups adjacent to each other constructed by communication apparatuses notifying beacons, the communication apparatuses can exchange necessary data between themselves, avoiding interference. Communication stations in a group set one beacon period to operate the network group. A communication station in the group acquires a beacon period and a reservation period of an adjacent group, sets its own reservation period avoiding the acquired beacon period and reservation period, and as necessary, enters the adjacent group to exchange necessary data. A device shared by a plurality of users does not belong to any group, and a communication apparatus in a different group temporarily enters the beacon period as necessary to exchange data.