A communication apparatus includes a communication connector, a communication section, a connection section, a state detector, a controller and a warning section. The communication section controls communication performed through the communication connector, to which a communication plug is connected. The connection section connects the communication connector and the communication section. The state detector generates a state detection signal corresponding to a connection state of the communication plug relative to the communication connector. The controller determines which of a normal connection state, an improper connection state and a non-connection state the communication plug is in based on the state detection signal. The controller also controls an ON-OFF operation of the connection section. The warning section notifies a user of results determined by the controller.