A communication system comprising: a control line transmitting a control signal for controlling charging of a battery mounted on a vehicle; a reference potential line connected to a reference potential; a communication device connected to the control line and the reference potential line serving as a transmission medium of a differential signal and superposing onto the control signal the differential signal having a higher frequency than the control signal so as to perform communication with an external power supply apparatus; and a first inductive element which is provided at a point of connection between the reference potential line and the reference potential or provided in the reference potential line, the first inductive element having impedance for a noise having a higher frequency than the control signal is higher than the impedance for the control signal; characterized in further comprising: a wire for connecting the communication device to another battery; and a second inductive element which is provided at a point of connection between the wire and the other battery or provided in the wire, the second inductive element having impedance for a noise having a higher frequency than the control signal that is higher than the impedance for the control signal; wherein the first inductive element and the second inductive element are arranged to suppress that a common mode noise generated in the control line and the reference potential line is converted into a differential mode noise; and wherein the first inductive element is a choke coil, and wherein no choke coil is provided in the control line. a control line transmitting a control signal for controlling charging of a battery mounted on a vehicle; a reference potential line connected to a reference potential; a communication device connected to the control line and the reference potential line serving as a transmission medium of a differential signal and superposing onto the control signal the differential signal having a higher frequency than the control signal so as to perform communication with an external power supply apparatus; and a first inductive element which is provided at a point of connection between the reference potential line and the reference potential or provided in the reference potential line, the first inductive element having impedance for a noise having a higher frequency than the control signal is higher than the impedance for the control signal; characterized in further comprising: a wire for connecting the communication device to another battery; and a second inductive element which is provided at a point of connection between the wire and the other battery or provided in the wire, the second inductive element having impedance for a noise having a higher frequency than the control signal that is higher than the impedance for the control signal; wherein the first inductive element and the second inductive element are arranged to suppress that a common mode noise generated in the control line and the reference potential line is converted into a differential mode noise; and wherein the first inductive element is a choke coil, and wherein no choke coil is provided in the control line. a wire for connecting the communication device to another battery; and a second inductive element which is provided at a point of connection between the wire and the other battery or provided in the wire, the second inductive element having impedance for a noise having a higher frequency than the control signal that is higher than the impedance for the control signal; wherein the first inductive element and the second inductive element are arranged to suppress that a common mode noise generated in the control line and the reference potential line is converted into a differential mode noise; and wherein the first inductive element is a choke coil, and wherein no choke coil is provided in the control line.