An apparatus and a system for automatically tracking data speed are disclosed. An embodiment of the invention provides a transmitting apparatus for automatically tracking data speed that includes: an encoder configured to convert parallelized input data according to a preset signal rule into a first signal and a second signal, where the input data is inputted as a unit of n bits, the encoder outputs the first signal and the second signal such that, if the input data includes identical bit values consecutively, one of the first signal and the second signal is converted to include transition information instead of following a differential rule with respect to the other signal; a serializer configured to serialize the first signal and the second signal; and a transmitting part configured to transmit the serialized first signal and second signal.