The exchange device groups PON branches into PON branch groups based on the amount of communication data traffic that has arrived via a communication network with a plurality of optical network units (ONUs) respectively belonging to one of a plurality of PON branches as a transmission destination, multiplexes the communication data for each PON group, and transmits the multiplexed data. The exchange device has an unit configured to transmit each piece of communication data from the ONUs to one output port selected from among a plurality of output ports based on the transmission wavelength of the communication data. The exchange device groups a plurality of PON branches into PON branch groups based on the required bandwidth of each of the ONUs, and designates the transmission wavelength for each of the ONUs so that each piece of the communication data from one PON branch group is transmitted to one port.