A communication apparatus for use in a vehicle includes a transmission repeater, a transmission terminator and a re-number unit. In a wireless communication between the communication apparatus and a communication unit in a facility such as a toll collection booth or the like, the transmission repeater transmits transmission data to the communication unit repeatedly until receiving an acknowledgement of reception completion of the transmission data from the communication unit, and the transmission terminator terminates repeated transmissions of the transmission data by the transmission repeater when a number of the repeated transmissions of the transmission data reaches a standard value. Further, the re-number unit changes the number of the repeated transmissions of the transmission data based on a content of the transmission data from the communication unit.