A communication system including a first and second communication apparatus is provided. The first communication apparatus includes first communication means for communicating with the second communication apparatus using the system information, and first setting means for setting the system information in the first communication means. The second communication apparatus includes second communication means for communicating with the first communication apparatus using the system information, and second setting means for setting the system information in the second communication means. The system information is commonly determined for all of the first and second communication apparatuses. The first and second setting means exchange new system information inputted by a user or given in advance with the second or first communication apparatus after communication is established, and set the new system information in the first or second communication means, respectively.