The present invention relates to an apparatus and method of converting data to display smooth and vivid images and to improve the gray scale use efficiency. The apparatus of converting data includes a gray scale detector that that generates a gray scale detection signal and a gray scale change signal by detecting a same gray scale, from an M bit input data, in a plurality of pixels adjacent to one another. The apparatus of converting data further includes a gray scale corrector that generates an N bit data by correcting one of the same gray scale according to the gray scale detection signal and the gray scale change signal output from the gray scale detector, wherein N and M are integers, N being larger than M.