A radio communication system by which an additional terminal can be easily registered to group information to set up radio communication between particular terminals, and a new user can conduct radio communication in a short period of time. When a group application request to establish radio communication between POC terminals is received, a CUG server creates a group table, generates group information by assigning group identification information to the group table, and stores the group information in the server. The CUG server then delivers the group identification information to a host POC terminal. When a registration request to the group table and group identification information are received from a POC terminal, the CUG server retrieves a group table assigned with the group identification information received from the POC terminal to automatically register terminal identification information of the POC terminal as the registration request source to the group table.