If frequency band (channel) expansion is made without careful consideration, communications of other apparatuses are disturbed. An apparatus which belongs to an identical network before expansion of the frequency band may no longer be able to make a communication after expansion of the frequency band. To accomplish this, upon making communications using a plurality of channels, a communication apparatus of a network probes the presence of other networks, requests other communication apparatuses of the network to make communication using the plurality of channels based on the probe result, and makes communication using the plurality of channels based on responses to the request. Upon making communications using neighboring channels, the communication apparatus probes the presence of networks in neighboring channels and channels that neighbor the neighboring channels, and makes communications using a used channel and the neighboring channel.