In an RF device, an RF circuit includes at least two RF transmitting/receiving elements; and an RF switch controlled to selectively electrically couple to one of the RF transmitting/receiving elements for transmitting/receiving an RF signal in response to a control signal. In addition, a testing circuit includes a first filter unit having a first external terminal electrically coupled to a testing signal and a second external terminal electrically coupled to the RF circuit, wherein the first filter unit is configured to allow the testing signal to enter the RF circuit while blocking an RF signal transmitted in the RF circuit from entering the testing circuit; and a testing-result informing unit having an external input electrically coupled to the first external terminal, and determining contents of the control signal according to an electric level at the external input.