A radio-frequency identification reader device including a plurality of antennas, a switch module, a coaxial cable, and a reader is provided. The switch module is electrically connected to the antennas. The coaxial cable is electrically connected to the switch module. The reader transmits a DC voltage, a control signal, and a radio-frequency signal to the switch module through the coaxial cable. The switch module generates an operation voltage by the DC voltage and the control signal. The switch module selects one of the antennas as a preset antenna by the control signal and drives the preset antenna by the radio-frequency signal.