A digital broadcasting system and a data processing method are disclosed. A receiver receives a broadcast signal including mobile service data and main service data. A known data detector detects known data from the broadcast signal. An equalizer performs channel equalization on the mobile service data received by means of the detected known data. An RS frame decoder acquires an RS frame from the channel-equalized mobile service data. A management processor extracts a Generic Stream Encapsulation (GSE) packet from a GSE Base Band (BB) constructing one row of the RS frame, and calculates an IP datagram from the extracted GSE packet. A presentation processor displays broadcast data using data contained in the calculated IP datagram.