A method of distributing group identifiers IDs (GIDs) in a power line communication (PLC) network, a method of receiving the GIDs, an authentication apparatus, and a PLC apparatus are provided. The authentication apparatus includes: an authentication mode storing unit which stores an authentication mode having a value including one of an authentication authorized mode and an authentication unauthorized mode; a GID request receiver which receives a GID request message from a PLC apparatus; and a GID transmitter which, if the authentication mode is the authentication authorized mode, transmits a GID corresponding to the PLC apparatus to the PLC apparatus. Authentication is realized in a PLC media access control layer distributing the GIDs between a PLC apparatus and an authentication apparatus, so manually inputting a GID into the PLC apparatus is not necessary. Further, the GIDs are distributed via the authentication apparatus, thereby centrally managing the GIDs.