1. An image inspection apparatus that performs comparison between a reference image and an inspection image obtained by performing 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 that compares 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 that detects 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 that compares the line image detected from the reference image with the line image extracted from the inspection image to perform inspection; and a determining unit that determines 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.