An object of the present invention is to apply a phase shift method to a workpiece having a rough surface to accurately detect an abnormal concave-convex irregularity. Therefore, in an inspecting system of the present invention, an image of a stripe pattern reflected on an inspection target surface is detected at a shallow angle, and one or more continuous unit stripes of a unit stripes reflected image is specified among from the stripe pattern reflected images existing in a predetermined distance range counted from the edge in a closer side to the workpiece. Then, the phase of the specified unit stripes reflected image is varied to apply a phase shift method and scan the inspection target surface with the unit stripes reflected image to thereby detect the abnormal concave-convex irregularity.