A relaying device comprising: a network communication unit for communicating with a terminal device over a network; a control unit for controlling the communication with the terminal device; and a storage unit in which a group table is stored, wherein in the group table, a normal group (0010, 0011) in which the terminal device is registered in advance, and a user group (1000, 1001) in which the terminal device belonging to the normal group (0010, 0011) is registered as a belonging terminal device according to the request from the terminal device belonging to the normal group (0010, 0011) are set, for each of the normal group (0010, 0011) and the user group (1000, 1001), a group ID (0010, 0011, 1000, 1001) and a terminal ID (1, 2, 3, 4, 5, 6, 7) of the terminal device belonging to the group are registered, when the control unit receives a voice signal of a group communication from the terminal device, the control unit is configured to transfer the voice signal to another terminal device belonging to the group to which the terminal device belongs, characterized in that for each of the normal group (0010, 0011) and the user group (1000, 1001), a group type (NORMAL, USER) is registered, and when the control unit receives registration request information for requesting registration to the user group (1000, 1001) from the terminal device belonging to the normal group (0010, 0011), the control unit is configured to register the terminal device belonging to the normal group (0010, 0011) in a specified user group (1000, 1001) as the belonging terminal device and to temporarily delete the terminal device belonging to the normal group (0010, 0011) from the normal group (0010, 0011) to which the terminal device belongs a network communication unit for communicating with a terminal device over a network; a control unit for controlling the communication with the terminal device; and a storage unit in which a group table is stored, wherein in the group table, a normal group (0010, 0011) in which the terminal device is registered in advance, and a user group (1000, 1001) in which the terminal device belonging to the normal group (0010, 0011) is registered as a belonging terminal device according to the request from the terminal device belonging to the normal group (0010, 0011) are set, for each of the normal group (0010, 0011) and the user group (1000, 1001), a group ID (0010, 0011, 1000, 1001) and a terminal ID (1, 2, 3, 4, 5, 6, 7) of the terminal device belonging to the group are registered, when the control unit receives a voice signal of a group communication from the terminal device, the control unit is configured to transfer the voice signal to another terminal device belonging to the group to which the terminal device belongs, characterized in that for each of the normal group (0010, 0011) and the user group (1000, 1001), a group type (NORMAL, USER) is registered, and when the control unit receives registration request information for requesting registration to the user group (1000, 1001) from the terminal device belonging to the normal group (0010, 0011), the control unit is configured to register the terminal device belonging to the normal group (0010, 0011) in a specified user group (1000, 1001) as the belonging terminal device and to temporarily delete the terminal device belonging to the normal group (0010, 0011) from the normal group (0010, 0011) to which the terminal device belongs