There are provided a dual mode communications device and a method of improving a data rate thereof. The dual mode communications device according to the embodiment of the present invention may include a selection unit 100 connecting antenna terminals to receive terminals or transmit terminals, a receive path circuit unit allowing RF receive signals from each of the first and second antennas to pass therethrough, a transmit path circuit unit providing RF transmit signals to the transmit terminals of the selection unit, an RF circuit unit converting the RF receive signals from the receive path circuit unit into baseband signals and converting the baseband signals to be transmitted into the RF transmit signals, and a baseband circuit unit performing control and signal processing of the selection unit in a single communications mode among a dual mode and a single mode.