A main display section is divided into a plurality of display areas (partial display areas). In each display area, image correction is carried out according to individual correction parameters. A target image for image correction is displayed in an image display area as a single image in a state that each section displayed in each display area has been corrected by using different parameters. In response to moving an indicator, which is displayed on an upper side of the main display section, along a slide bar, a size and a position of each display area is changed. An area size display bar, which shows a display range of each display area, is displayed on the upper side of the main display section. When one display area is selected for inputting the correction parameters, a section of the area size display bar, which corresponds to the selected display area, is highlighted.