A data transmitter includes: a packetization unit receiving primary data from a data processor and packetizing the primary data; a high-speed transmission unit transmitting a data packet obtained from the packetization to a display device in a high-speed mode; and a low-speed transmission unit relaying and transmitting secondary data between the data processor and the display device in a low-speed mode. Accordingly, it is possible to transmit and receive data rapidly and efficiently.