An image processing device includes: an analysis unit to analyze vector image data including line information and area color information; a detection unit to detect a boundary pixel through which an outline passes; a determination unit to determine whether the outline passes longitudinally through the boundary pixel; and a coloring unit to sequentially fill each pixel on a scan line. A color of a target pixel is calculated based on the area color information and the target pixel is filled with the calculated color when the target pixel is a boundary pixel. A reference filling color is changed from the first color to the second color defined for a target pixel when the target pixel is a boundary pixel through which an outline passes longitudinally. A target pixel is filled with the reference filling color when the target pixel is not a boundary pixel.