To provide a splitter which makes an electric lamp cord (power line) or a coaxial cable available as a transmission line for communication at the same time and automatically selects only the coaxial cable as a transmission line.

A splitter (slave unit) 10a comprises a PLC jack t3 and electric lamp cord jack t5 for inputting/outputting a PLC signal, and a coaxial cable jack t4 for inputting/outputting a communication signal in which an AC commercial power supply is canceled from the PLC signal. Between the PLC jack t3 and the electric lamp cord jack t5, a switch 6 is provided which is capable of selecting a path through a filter (LPF 5) that shuts off the PLC signal ((b) side of the switch 6) and a path detouring the LPF 5 ((a) side of the switch 6). When the coaxial cable 14a is connected to the coaxial cable jack t4 and an fs detector 9 detects an fs signal, the fs detector 9 then operates the switch 6 to select the (b) side and only the coaxial cable 14 is selected as a communication path without using an electric lamp cord 12.