A radio-communication terminal device having an antenna unit incorporating an antenna element and an authenticator for authenticating the connected antenna element, and a transceiver unit that includes a transmission circuit, a reception circuit, an authentication detector and a communication controller. The antenna unit further includes a first antenna connector and a first connector. The transceiver unit includes a second connector that connects to the first connector when the first antenna connector connects to the second antenna connector. The authentication detector detects the authentication of the authenticator when the first connector is connected to the second connector. The communication controller prevents the transmission circuit from transmitting signals when the authenticator cannot authenticate the connection to the antenna unit.