Disclosed is a digital television system carrying out modulation/demodulation by VSB (vestigial side band). A VSB transmitter includes an additional error correction encoder designed in a manner that a signal mapping of a TCM encoder is considered, a multiplexer (MUX), a TCM encoder operating in a manner corresponding to state transition processes of the additional error correction encoder, and a signal transmission part including an RF converter. And, A VSB receiver includes a signal receiver part receiving a signal transmitted from the transmitter, a TCM decoder, a signal processing part including a derandomizer, and an additional error correction decoder part.