Provided is a method of decoding a low-density parity-check code (LDPC). The decoding method including an initialization process, a check node update process, a variable node update process, a tentative decoding process, and a parity check process, for a plurality of check nodes and a plurality of variable nodes, further includes detecting at least one inactive variable nodes that do not require variable node update among the variable nodes, the variable node update process is performed only on active variable nodes except for the inactive variable node, and the check node update process is performed without using the inactive variable node.