Disclosed is an apparatus for converting data capable of enhancing sharpness without deterioration of picture quality, and a display apparatus using the same, wherein the apparatus for converting data is provided in the display apparatus with a plurality of unit pixels, each unit pixel with red, green, blue and white sub-pixels, and the apparatus for converting data includes a 4-color data generator for generating 4-color data of red, green, blue and white colors for each unit pixel based on 3-color input data of red, green and blue colors of an input image; and a sharpness enhancer for enhancing sharpness of the input image by correcting white sub-pixel data of the unit pixel corresponding to an edge portion of the input image by a luminance variation of adjacent unit pixels based on white sub-pixel data for each unit pixel.