The invention discloses a hue dividing and judging device including a memory unit, a calculation module, and a judgment module. The memory unit is used for storing a look-up table, and the look-up table records N boundaries, wherein the N boundaries includes j+1 operative boundaries for defining j color areas. The calculation module is used for calculating the hue of each pixel of an input image. According to the look-up table, the judgment module is used for judging where the hue of each pixel falls within two of the operative boundaries, so as to judge that the hue of the pixel of the input image falls into which one of the color areas. Accordingly, if there are more operative boundaries recorded in the look-up table, the hue will be divided into more color areas, and the user will have more choices for adjusting the color of the input image.