There is provided a technique to make, in a case where a monochrome image is generated based on a color image, a chromatic image region on the color image distinguishable on the monochrome image. There are included a first image reading unit to acquire monochrome image data by reading an image in monochrome from an original document, a second image reading unit to acquire color image data by reading an image in color from an original document, an extraction image generation unit to generate image data by extracting a chromatic image region in the color image data read by the second image reading unit, and a luminance correction unit to make a correction to increase, based on the image data generated by the extraction image generation unit, luminance of a monochrome signal which is included in the monochrome image data read by the first image reading unit and corresponds to the chromatic image region extracted by the extraction image generation unit.