A digital broadcast transmitter comprising: a randomizer to receive a data stream of which stuff bytes are inserted into a specified position and to randomize the received data stream; a stuff-byte exchange unit to generate known data having a predefined pattern and to insert the known data into the specified position of the data stream into which the stuff bytes are inserted; an encoder to encode the data stream output from the stuff-byte exchange unit for an error correction; and a modulator and RF converter to modulate the encoded data stream, RF-convert the modulated data stream and transmit the RF-converted data.