An inspection apparatus to precisely quantitatively inspect positions of formation of film layers formed on the surface of a disk-shaped substrate. It generates captured image data expressing a captured image corresponding to a field of vie based on image signals successively output from an image capturing unit capturing an image of a predetermined surface at an outer circumference part of the disk-shaped substrate and generates film layer edge position information expressing longitudinal direction positions at corresponding positions along the circumferential direction of an edge line of a film layer image pan corresponding to the film layer on the surface image with reference to, from the captured image data, longitudinal direction positions at the different positions along the circumferential direction of a boundary line between a surface image part corresponding to the predetermined surface on the captured image and its outer image part.