A group communication method capable of performing group communication without additional functions provided on a network and with preventing excessive network traffic. Each communication device first transmits an enrollment message. A providing device groups the communication devices, creates a group key specifying the communication devices that are identified as a same subgroup, and transmits the group key to the communication devices. The communication devices receive and store the group key. To transmit distribution data to a subgroup, the providing device transmits the data together with data corresponding to the group key to a selected communication device of the subgroup. When the communication devices recognize the distribution data, the communication devices determine whether to receive the distribution data, based on the distribution data and the stored group key.