A communication system that transmits and receives a message including an amount of data and an identifier determined for the contents of each data. The communication system includes a device that receives the message and includes an processor that processes data in the message, a detector that detects a vehicle situation, and an storage that stores attributes, wherein the storage stores an identification code, 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 processor acquires, based on a combination of the identification code corresponding to the identifier of the received message and the situation code corresponding to the vehicle situation detected by the detector, an attribute corresponding to the combination among the attributes stored in the storage, and processes data of the received message based on the acquired attribute.