Provided is an image sharpening processing device capable of performing image sharpening processing by changing only luminance without changing a hue. The image sharpening processing device includes: a smoothing means for smoothing luminance of an input image and thus obtaining a smoothed image; a subtraction means for subtracting the smoothed image from the luminance of the input image and thus obtaining a difference image; a luminance-linked gain calculation means for calculating a luminance-linked gain from the input image; a first multiplication means for multiplying the difference image by the luminance-linked gain and thus obtaining a multiplication result; an addition means for adding the multiplication result to the luminance of the input image and thus obtaining luminance of an output image; a color difference gain calculation means for calculating a color difference gain from a color difference of the input image and the luminance-linked gain; and a second multiplication means for multiplying the color difference of the input image by the color difference gain and thus obtaining a color difference of the output image.