1. An image processing device comprising: a hardware processor which is configured to perform: an isolated point noise detection process that detects an isolated point noise that is included in an image; and an isolated point noise correction process that corrects the isolated point noise detected by the isolated point noise detection process, wherein the isolated point noise detection process includes an isolated point noise presence/absence determination process and an attention pixel isolated point noise determination process, wherein the isolated point noise presence/absence determination process determines whether or not the isolated point noise is included within a given area based on a first index value that represents a range of first to nth pixel values, and a second index value that represents a range of a pixel value group, the given area including an attention pixel that is an isolated point noise detection target, the first to nth pixel values being obtained by arranging pixel values of pixels within the given area in ascending or descending order, and the pixel value group being obtained by excluding at least one of the first pixel value and the nth pixel value from the first to nth pixel values, and wherein the attention pixel isolated point noise determination process determines whether or not the attention pixel is a pixel that corresponds to the isolated point noise when it has been determined that the isolated point noise is included within the given area.