A power line communication system which enables high quality communication utilizing a pair of power lines connected to a vehicle mounted battery, has a pair of communication lines connected to a pair of power lines, respectively, to communicate a high frequency signal of 1 MHz or more. This system has a balance filter which is interposed between each of the communication lines and a vehicle mounted communication apparatus, the filter, a circuit configuration of which is formed in balance type. The communication system also has a pair of electrically balanced lines which are connected between the balance filter and each of the communication apparatuses and are power-fed from the battery, for performing communication between the communication apparatuses.