A digital broadcasting system and a data processing method thereof are provided. An apparatus for generating a transport stream includes a packet generator for generating a plurality of packets by compressing video and audio signals; a counter for counting the number of the generated packets and outputting the count result; and an information controller for determining whether the count result of counting reaches a predetermined number of packets, inserting packet start information into the packets according to the count result, and transmitting the packets with the packet start information inserted therein. The packet start information is added to a packet to be transmitted in a transmitter, and the packet start information is extracted from the received packet in a receiver, so that the waste of frequency resources can be reduced.