To provide power line carrier communication equipment by which communication is performed even in the case that power is not supplied.

This power line carrier communication equipment 3 capable of communicating signals having external equipment via a power line 4 as a power supply line from an external power source is provided with an internal power source 8, a power source part 6 receiving the supply of the power from the external power source provided with a power-monitoring function 7 monitoring the power supply state of the external power source, and communication parts 9, 10 and 11 for controlling signal communication. The power source 6 changes the supply source of the power from the external power source to the internal power source 8, when insufficient power supply from the external power source occurs.