To increase a service class band without increasing the number of fibers in a network, and prevent interference between a plurality of service classes.

Packet interfaces 14, 24 in wavelength multiplexers 10, 20 provide input port information to an input packet. Identifier table searchers 15, 25 specify a service class to which the packet belongs on the basis of the input port information. Wavelength mappers 16, 26 map the packet to a frequency corresponding to the service class to which the packet belongs. WDM network interfaces 17, 27 multiplex the wavelength and output it to a WDM network 30.