A method is provided for transmitting a Low Density Parity Check (LDPC) code by a signal transmission apparatus in a multimedia system. The method includes generating the LDPC code based on a resulting parity check matrix, which is generated by performing a scaling down operation on a base parity check matrix; and transmitting the LDPC code. The scaling down operation is performed based on a scaling factor for determining a size of each permutation matrix in the resulting parity check matrix and a size of each zero matrix included in the resulting parity check matrix, and the scaling factor is determined based on a number of column blocks included in the base parity check matrix and a size of each permutation matrix included in the base parity check matrix.