1. An inspecting device comprising: a read image acquirer configured to acquire a first read image that is obtained by reading a printed matter; a reference image generator configured to generate a reference image based on a source image from which the printed matter has been generated; an inspector configured to inspect the printed matter based on threshold information containing one or more types of thresholds and based on a difference image indicating a difference between the first read image and the reference image; an identifier configured to identify, on the printed matter, an area having a discrepancy between an inspection result and a result of visual check by a user; and a changer configured to change the threshold information to resolve the discrepancy in the area.