In order to detect a local shape defect on an inner surface of an ordinary plane member with a high degree of accuracy as a state distinguished from a big waviness deformation, a surface-shape-defect inspecting method and apparatus for identifying the shape defect on the inner surface of the plane member is provided. The method and apparatus provides for scanning optically the entire area of the plane member, extracting a shape of the surface of the plane member as absolute height displacement data at scanning positions, finding a difference between a reference surface shape inferred from the extracted shape of the surface of the plane member and the shape of the surface, and using the difference as relative height displacement data with respect to the reference surface shape, and detecting the shape defect on the surface by identifying the location of the shape defect through comparison of the relative height displacement data with predetermined allowable displacement.