To realize a hybrid coupled circuit that does not use a transformer.

A driving signal corresponding to a transmission signal from a transmitting terminal Ti is generated by a photocoupler driving circuit having an amplifier 52b, and a photocoupler 51 makes current corresponding to the transmission signal flow through a line via terminals L1 and L2. A driving signal corresponding to voltage on the line is generated by a photocoupler driving circuit 54, and a photocoupler 53 to which the driving signal is inputted outputs current corresponding to the voltage on the line. An output current of the photocoupler 53 is converted into voltage by current/voltage conversion circuit 55, and a direct current component is cut by a capacitor 56. An addition circuit 57 extracts a received signal alone from a voltage signal given from the capacitor 56 by canceling a transmission signal part on the terminal Ti and gives the received signal to a receiving terminal To.