An outer encoder includes a bit detector that receives a turbo stream provided with a parity insertion region and that detects data bits from the turbo stream, an encoder that convolution-encodes the detected data bits, and a bit inserter that inserts an encoded value outputted from the encoder into the parity insertion region in the turbo stream. The encoder includes a first register; a second register, in which when a bit value is stored in the first register, a stored value pre-stored in the first register is shifted and stored; a third register, in which when a bit value is stored in the second register, a stored value pre-stored in the second register is shifted and stored; a first adder adding the input bit value, the stored value pre-stored in the first register, and the stored value pre-stored in the third register, and storing the resultant value of addition in the first register, if a specified bit is inputted; and a second adder adding the input bit value, the stored value pre-stored in the first register, and the stored value pre-stored in the second register to output the resultant value of addition. Accordingly, only the turbo stream in the dual transport stream is robustly processed.