Disclosed is an apparatus for transmitting a bit-interleaved coded modulation (BICM) signal in an orthogonal frequency division multiplexing (OFDM) system. A serial-to-parallel (S/P) converter generates bit streams using coded bits according to the number of transmission antennas and a modulation order of a predetermined modulation scheme. An interleaver applies at least one offset to the bit streams and performs interleaving on the offset-applied bit streams. A combiner combines the interleaved bit streams according to the number of transmission antennas.