The present disclosure relates to a pre-5th-generation (5G) or 5G communication system to be provided for supporting higher data rates beyond 4th-generation (4G) communication system such as a long term evolution (LTE). A method includes decoding a codeword corresponding to a preset decoding scheme to detect reliability information of each of codeword bits included in the codeword, wherein at least one of a number of quantization bits and a range of a quantization level used for detecting reliability information in the decoding scheme is determined based on a degree of a node on a bipartite graph of a low density parity check (LDPC) code.