An apparatus for bidirectional communication between multi-nodes using a relay node receives 2M signals, encoded using a nested lattice code chain, from a base station and M user nodes in a predetermined time interval, estimates M pairwise lattice code sum signals between the base station and the M user nodes based on the nested lattice code chain with respect to the 2M encoded signals, encodes the M pairwise lattice code sum signals to broadcasting codewords to generate M encoded signals after the predetermined time interval has ended, and transmits the M encoded signals to the base station and the M user nodes.