A communication system that is configured to transmit and receive a communication message including a defined amount of data and an identifier determined for each of the contents of data, the communication system comprising a communication device that is configured to receive the communication message and that includes an information processing unit that is configured to process data in the communication message, a vehicle situation detection unit that is configured to detect a vehicle situation, wherein the vehicle situation is one of normal travel, during right turn, during left turn or high-speed travel, and an attribute storage unit that stores attributes, wherein the attribute storage unit stores an identification code corresponding to the identifier, a situation code determined according to the vehicle situation, and an attribute determined corresponding to a combination of the identification code and the situation code as the attribute, and the information processing unit is configured to acquire, based on a combination of the identification code corresponding to the identifier of the received communication message and the situation code corresponding to the vehicle situation detected by the vehicle situation detection unit, an attribute corresponding to the combination among the attributes stored in the attribute storage unit, and to process data of the received communication message based on the acquired attribute, wherein the attribute includes a plurality of elements, wherein the elements are selected from category, importance and expiration date, wherein the communication device that is configured to receive the communication message includes a data storage unit in which data is held in a determined address for each piece of data acquired from the received communication message, and an identification code stored in the attribute storage unit is determined based on an address of the data storage unit in which data of a corresponding communication message is held. a communication device that is configured to receive the communication message and that includes an information processing unit that is configured to process data in the communication message, a vehicle situation detection unit that is configured to detect a vehicle situation, wherein the vehicle situation is one of normal travel, during right turn, during left turn or high-speed travel, and an attribute storage unit that stores attributes, wherein the attribute storage unit stores an identification code corresponding to the identifier, a situation code determined according to the vehicle situation, and an attribute determined corresponding to a combination of the identification code and the situation code as the attribute, and the information processing unit is configured to acquire, based on a combination of the identification code corresponding to the identifier of the received communication message and the situation code corresponding to the vehicle situation detected by the vehicle situation detection unit, an attribute corresponding to the combination among the attributes stored in the attribute storage unit, and to process data of the received communication message based on the acquired attribute, wherein the attribute includes a plurality of elements, wherein the elements are selected from category, importance and expiration date, wherein the communication device that is configured to receive the communication message includes a data storage unit in which data is held in a determined address for each piece of data acquired from the received communication message, and an identification code stored in the attribute storage unit is determined based on an address of the data storage unit in which data of a corresponding communication message is held.