An optical compensation method for an organic light emitting display device comprises: setting initial gain values of RGB subpixels; making each of the RGB subpixels converge on target luminance; selecting subpixels to emit light with the W subpixel from the RGB subpixels, and setting an initial gain value of the W subpixel; measuring color coordinates and luminance of the W subpixel to which the initial gain value is applied; calculating the luminance ratio of the W subpixel and the selected subpixels; adjusting maximum gains of the W subpixel and the selected subpixels; measuring maximum color coordinates and luminance ratio of the W subpixel and the selected subpixels; and making the W subpixel and the selected subpixels converge on target color coordinates and luminance.