Charging communication system, charging control unit and charging station

For a charging communication system wherein a charging control unit performs communications between an electric vehicle and a charging station by using a signal line in a charging cable, the electric vehicle (1) is equipped with a first communication unit (11) and a second communication unit (12) that use the same signal line in the charging cable (2) to communicate with the charging station (3), and a signal line connection unit (15) that switches between connection and disconnection between the second communication unit (12) and the signal line. The charging control unit (13), which controls a battery (10) of the electric vehicle (1), calculates an amount of voltage change in the signal line with respect to before and after the second communication unit (12) is connected to the signal line by the signal line connection unit (15), and disconnects the second communication unit (12) from the signal line by means of the signal line connection unit (15) if the amount of change is out of a predetermined allowable range.