A base station control portion selects one or multiple signals in accordance with the state of radio waves from signals received through multiple communication paths. A wireless communication apparatus communicates with a wireless terminal and a wired communication network at multiple frequencies. In response to a request for software upgrading from a network management device, the wireless communication apparatus selects one frequency, controls the state of transmission waves of a wireless interface such that a communication path in which a communication service is being provided can be switched to another communication network without interruption, rewrites software for each wireless interface to software received through a wired interface in advance, and returns the state of transmission waves of the wireless interface. Thus, the software can be upgraded without blackouts of the communication service to the wireless terminal.