An RF signal receiving apparatus includes a first poly-phase filter, a second poly-phase filter, a first frequency-mixer module, a switch and a low-pass filter module. The first poly-phase filter receives an RF input signal and produces a filtered RF signal according to the received RF input signal. The first frequency-mixer module conducts frequency-mixing operation on a reduced-frequency signal and the filtered RF signal to produce a plurality of reduced-frequency RF signals. The switch receives and transmits the reduced-frequency RF input signal to a first channel or a second channel according to a selection signal. The second poly-phase filter receives the reduced-frequency RF signal transmitted by the second channel and filters the received signal. The low-pass filter module receives the filtered reduced-frequency RF signal or the reduced-frequency RF signal transmitted by the first channel to conduct low-pass filtering operation and produces a low-intermediate-frequency signal or a zero-intermediate-frequency signal.