Provided are a communication system and a communication device capable of suppressing attenuation of a communication signal superimposed upon a control pilot line. This output circuit (20) sends a control pilot signal which has been generated at a voltage generation source (21) to an input circuit (60). Between the control pilot line (4) and the ground line (3) of the output side of the output circuit (20), a communication unit (30) is connected via a transformer (31). Between the control pilot line (4) and the ground line (3) of the input side of the input circuit (60), a communication unit (70) is connected via a transformer (71). Between the output circuit (20) and the transformer (31), a lowpass filter (33) is interposed. Between the input circuit (60) and the transformer (71), a lowpass filter (73) is interposed.