A data transmitting device and a flat plate display using the same are disclosed. The data transmitting device includes a clock generator to generate and output a first clock signal and to generate a plurality of second clocks signals having different phases; a serializer to convert parallel image data and a dot clock input at a slow speed to high speed serial data and high speed clock according to the first and second clocks outputted from the clock generator and to output the high speed serial image data and the high speed clock; and a signal converter to convert the serial image data and the high speed clock outputted from the serializer into differential signals and to output the differential signals.