1. An inspection apparatus of a disk-shaped substrate having film layers formed on its surface, which has an image capturing unit having a capturing view field including a predetermined surface at an outer circumference part of said disk-shaped substrate, successively capturing images of said predetermined surface in a circumferential direction of said disk-shaped substrate, and outputting image signals and an image processor processing the image signals successively output from said image capturing unit; said image processor having an image data generating means for generating captured image data expressing a captured image corresponding to said capturing view field extending corresponding to the circumferential direction of said disk-shaped substrate based on said image signals and a film layer edge position information generating means for generating film layer edge position information from said captured image data using as a reference longitudinal direction positions showing positions in a direction traversing said circumferential direction at respective positions along said circumferential direction of a boundary line between a surface image part corresponding to said predetermined surface on said captured image and its outer image part, said film layer edge position information expressing longitudinal direction positions at corresponding positions along said circumferential direction of edge lines of film layer image parts corresponding to said film layers on said surface image part, wherein said film layer edge position information generating means has a means for detecting the longitudinal direction positions at respective positions along said circumferential direction of a boundary line between said surface image part on said captured image and said outer image part, a means for detecting the longitudinal direction positions at respective positions along said circumferential direction of the edge line of said film layer image part on said surface image part, and a correcting means for correcting the detected longitudinal direction positions at the respective positions along said circumferential direction of the edge line of said film layer image part using as the reference the longitudinal direction positions at the corresponding positions along said circumferential direction of the boundary line between said surface image part and said outer image part, and generating said film layer edge position information, and wherein said film layer edge position information is used to evaluate positions of formation of said film layers at said disk-shaped substrate.