An image processing device includes a pattern kind determining unit that determines a hatch pattern representing a hatch shape corresponding to a color of a color image by a monochromatic concentration, a pattern concentration determining unit that determines a background concentration that is applied to a hatch-shaped background area, and a monochromatic image data generating unit that generates monochromatic image data in which the hatch pattern having the background concentration is applied to the background area. The pattern concentration determining unit changes the background concentration of the hatch pattern according to the color of the color image.