A digital television system performing modulation/demodulation by VSB (vestigial side band) is provided. The invention includes a VSB transmitter including an additional error correction encoder designed such that a signal mapping of a TCM encoder is considered, a multiplexer (MUX), a TCM encoder operating in correspondence with state transition processes of the additional error correction encoder, and a signal transmission part including an RF converter. The invention further includes a VSB receiver including 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.