a charge monitoring apparatus is mountable on or connectable to a vehicle which uses electrical power supplied from a battery on the vehicle for traveling . the charge monitoring apparatus includes a vehicle id holding portion that holds vehicle - side identification information which is uniquely allocated to each specific vehicle , a power - line communicating portion that performs a power line communication with an extravehicular apparatus through a power supply line which supplies the electric power from the external power supply equipment to the battery , a vehicle - side information storing portion that stores information produced in the vehicle , and a communication controlling portion that , in the power line communication , transmits the vehicle - side identification information held in the vehicle id holding portion to the extravehicular apparatus , and if predetermined condition is satisfied , the communication controlling portion transmits the information stored in the vehicle - side information storing portion to the extravehicular apparatus .