Provided are an apparatus and a method for generating a return-to-zero (RZ) signal, including: a first modulator receiving a first signal having a predetermined frequency to modulate, compensate for and output a first laser beam; a second modulator receiving a second signal complementary to the first signal to modulate, compensate for, and output a second laser beam; a mixer mixing signals output from the first and second modulators to output a third signal; and a third modulator modulating the third signal into an RZ signal and outputting the RZ signal.