To provide a communication apparatus for transmitting/receiving a signal via a power line through magnetic coupling between a signal line and the power line, a signal superimposing apparatus for superimposing the signal on the power line, and a signal extracting apparatus for extracting the signal from the power line.

A signal superimposing section 19 includes: an annular magnetic material 190; air gaps 192, 192 provided to a circumferential direction of the magnetic material 190; and the signal line 193 wound on the magnetic material 190, and the power line 2 is inserted to an insertion hole of the magnetic material 190. Further, a signal extracting section is configured similarly. The signal superimposing section 19 superimposes the signal transmitted from the communication apparatus from the signal line 193 to the power line 2 through the magnetic coupling between the signal line 193 and the power line 2 via the magnetic material 190. The air gaps 192, 192 provided to the magnetic material 190 prevent the magnetic material 190 from being saturated by a current flowing through the power line 2 and suppress the attenuation of the signal by the magnetic coupling.