An apparatus for inserting an error correction code according to an embodiment includes an identifier configured to identify a plurality of critical sets included in a codeword generated using a polar code, based on the number of information bits and a total code length of the codeword, a divider configured to divide the codeword into a plurality of partitions, and an inserter configured to insert an error correction code into each of the divided partitions based on a distribution position of each of the plurality of critical sets.