A priority control method includes receiving, by the server, the data to be subscribed by the terminal and the default priority of the data, and setting the terminal and the default priority in priority management information in association with each other, setting, by the server, the data issued by the data source and the terminal subscribing the data in subscriber management information in association with each other, transmitting, by the data source, an importance level of the issued data, setting, by the server, the importance level received from the data source in the priority management information in association with the default priority for the terminal subscribing the data; and referring, by the server, to the priority management information to calculate a final priority from the default priority for the terminal and the importance level.