An image processing device includes a specific color specification unit 2 for acquiring RGB color component data about specific colors a and b from a display image 5 by using a mark for specific color specification, a specific color information conversion unit 3 for determining values H respectively corresponding to the hues of the specific colors a and b from an RGB color space by using the RGB color component data about the specific colors a and b, and a color conversion unit 4 for color-converting the specific color a in the display image 5 into the specific color b according to the values respectively corresponding to the hues of the specific colors a and b.