To enable the effective inspection and measurement by the automation and avoid contaminating works to be inspected and measured by dispensing a light reflected from a measuring area being illuminated by an illuminating optical system into spectra in intersecting directions to specified direction and photographing a formed image.

A light emitted from a light source 10 is converted into a linear light source by a slit 12 and then into a collimated light by a lens 14, a beam splitter 16 reflects the collimated light from the lens 14 to irradiate a wafer 20 to be measured and optically couples a light reflected at the wafer 20 with a dispersion prism 22 which spatially disperses the light passed through a lens 18 and beam splitter 16, a lens 24 forms an image of the dispersed light on a light receiving face of a CCD camera 26, and a personal computer 28 inputs a signal outputted from the CCD camera 26 to convert into a tomographic image showing only the optical thickness in a z-axis direction perpendicular to an x-axis.