Provided is a Simple Aggregation Format (SAF) synchronization packet structure including an SAF synchronization packet header and an SAF synchronization packet payload and multiplexing diverse element streams. The header includes a field for providing time information needed when objects transmitted as a SAF synchronization layer packet payload compose a scene in a decoder; and the payload includes a field for providing information on the type of an access unit and a field for providing identification information of an elementary stream where the access unit belongs. Since the present invention can multiplex diverse elementary streams effectively and simply into one data stream, synchronized data transmission is possible. Since the present invention accommodates a synchronization layer packet of the MPEG-4 system, it can be easily integrated with the MPEG-4 system and utilize the advantage of the MPEG-4 synchronization layer packet such as the concept of an access unit or a degradation priority.