A transmitting apparatus includes: a low density parity check (LDPC) encoder configured to encode information bits to generate parity bits based on a parity check matrix according to a code rate of 8/15 and a code length of 64800; an interleaver configured to interleave an LDPC codeword including the information bits and parity bits; and a mapper configured to map the interleaved LDPC codeword onto constellation points, wherein the parity check matrix comprises an information matrix part corresponding to the information bits and a parity matrix part corresponding to the parity bits, and the information matrix part is defined by a specific table indicating indices of rows at which a value “1” is positioned in a 0-th column of an i-th column group in the parity check matrix.