A method and apparatus to efficiently transmit data. The method and apparatus effectively aggregate data and transmit the data in a high-speed power line communication (PLC) network. The method of transmitting the data includes combining each of at least one or more data units transferred from an upper layer, with a field to indicate attribute information of the data unit, dividing the combined data units and fields into frame blocks of an identical size, and aggregating the divided frame blocks and transferring the aggregated frame blocks as one frame to a PHY layer. In this way, data units of a variety of types and sizes transferred from the upper layer are aggregated and transmitted as the one frame.