To continue a communication without generating system down or regulating call origination/termination even if a congested state is generated by generating traffic exceeding the traffic volume processable in a wireless network system.

If a congested state is detected for a traffic processing apparatus 20-1, in a line multiplexing device 50, line switching processing is performed, so that at least a part of communication traffic to be processed by the relevant traffic processing apparatus 20-1 can be processed by another traffic processing apparatus 20-2.