A method of processing a digital broadcasting signal in a transmitter is provided. The method includes performing RS (Reed-Solomon) encoding on signaling data containing cross layer information between a physical layer and a upper layer, interleaving the RS encoded signaling data by writing the RS encoded signaling data row-by-row from left-to-right and top-to-bottom in a signaling data block and outputting the signaling data in the signaling data block by reading data column-by-column from top-to-bottom and left-to-right, and transmitting the digital broadcasting signal including the mobile service data and the interleaved signaling data during slots.