1. An image inspection apparatus configured to perform comparison between a reference image and an inspection image obtained by performing a scan of a printed medium on which the reference image has been printed, to determine whether the printed medium is acceptable, the image inspection apparatus comprising: a first inspecting unit configured to compare the reference image exclusive of an edge in the reference image with the inspection image exclusive of an edge in the inspection image to perform inspection; a line-image detecting unit configured to detect a line image inclusive of the edge in the reference image from the reference image, and a line image inclusive of the edge in the inspection image from the inspection image; a second inspecting unit configured to compare the line image inclusive of the edge in the reference image detected from the reference image with the line image inclusive of the edge in the inspection image detected from the inspection image to perform inspection; and a determining unit configured to determine whether the printed medium is acceptable based on a result of the inspection performed by the first inspecting unit and a result of the inspection performed by the second inspecting unit.