A power line communication system in which a vehicle and a feeding device are connected to each other with a charging cable (71, 72), and power line communication is performed between a power line communication device installed in the vehicle and the feeding device via the charging cable (71, 72), the charging cable (71, 72) comprising two power supply wires (71, 72), the power line communication device comprising: two internal power supply wires (11, 12) respectively connected to the power supply wires of the charging cable (71, 72); a filter circuit connected to and between the two internal power supply wires; and an electromagnetic guidance type signal converter comprising a primary coil provided in one or both of the internal power supply wires (11, 12), and a secondary coil electromagnetically connected to the primary coil, and the feeding device comprising: two internal power supply wires (51, 52) respectively connected to the power supply wires of the charging cable (71, 72); a filter circuit connected to and between the two internal power supply wires; and an electromagnetic guidance type signal converter comprising a primary coil provided in one or both of the internal power supply wires (51, 52), and a secondary coil electromagnetically connected to the primary coil, wherein a current loop circuit is formed by the two internal power supply wires (11, 12) and the filter circuit of the power line communication device, the two power supply wires of the charging cable (71, 72), and the two internal power supply wires (51, 52) and the filter circuit of the feeding device, and each of the power line communication device and the feeding device is configured to superpose a signal on the charging cable (71, 72) and extract a signal superposed on the charging cable (71, 72) by means of its signal converter (15, 55), the power line communication device comprises a connector device which is installed in the vehicle and to which the charging cable (71, 72) is connected, the connector device comprises: a plurality of connection terminals for connecting the connector device to the charging cable (71, 72); a connector body which houses the plurality of connection terminals; a plurality of internal wires including the two internal power supply wires (11, 12) and connected to the connection terminals; a tubular part which is provided in the connector body and through which the plurality of internal wires are inserted; an annular magnetic body provided externally around the tubular part; and a signal wire wound around the annular magnetic body, one or both of the internal power supply wires (11, 12) are wound around the annular magnetic body, and the electromagnetic guidance type signal converter of the power line communication device is formed by the annular magnetic body, the one or both of the internal power supply wires, and the signal wire. two internal power supply wires (11, 12) respectively connected to the power supply wires of the charging cable (71, 72); a filter circuit connected to and between the two internal power supply wires; and an electromagnetic guidance type signal converter comprising a primary coil provided in one or both of the internal power supply wires (11, 12), and a secondary coil electromagnetically connected to the primary coil, and two internal power supply wires (51, 52) respectively connected to the power supply wires of the charging cable (71, 72); a filter circuit connected to and between the two internal power supply wires; and an electromagnetic guidance type signal converter comprising a primary coil provided in one or both of the internal power supply wires (51, 52), and a secondary coil electromagnetically connected to the primary coil, wherein a plurality of connection terminals for connecting the connector device to the charging cable (71, 72); a connector body which houses the plurality of connection terminals; a plurality of internal wires including the two internal power supply wires (11, 12) and connected to the connection terminals; a tubular part which is provided in the connector body and through which the plurality of internal wires are inserted; an annular magnetic body provided externally around the tubular part; and a signal wire wound around the annular magnetic body,