A digital broadcasting system and a data processing method are disclosed. The receiving system of the digital broadcasting system includes a receiving unit, a main service data processor, a mobile service data processor, a controller, and an output controller. The receiving unit receives mobile service data and main service data including the same A/V broadcast signal and receives retransmission channel information. The main service data processor demodulates and error-corrects the received main service data and temporarily stores the processed data. The mobile service data processor demodulates and error-corrects the received mobile service data and temporarily stores the processed data. The controller generates and outputs a control signal based upon the received retransmission channel information and a receiving environment of the receiving system. And, the output controller selects any one of the A/V broadcast signal for the main service and the A/V broadcast signal for the mobile service based upon the control signal of the controller.