Even when an enlarged image is deteriorated due to a block noise or color mixture, the contour in the enlarged image is sharpened and a quality of the image is improved. A contour extracting unit 103 determines a pixel indicating the contour in an interpolation image, using brightness gradient strength and a brightness gradient direction. A contour correcting unit 104 specifies a first isolation pixel isolated by the predetermined distance from each pixel indicating the contour in a brightness gradient direction of the pixel indicating the contour and a second isolation pixel isolated by the predetermined distance from each pixel in a 180°-rotation direction of the brightness gradient direction, for each pixel indicating the contour, corrects colors of the pixels between the pixel indicating the contour and the first isolation pixel with a color of the first isolation pixel, and corrects the colors of the pixels whose colors are not corrected with the color of the first isolation pixel among the pixels between the first isolation pixel and the second isolation pixel with a color of the second isolation pixel.