1. An inspection device, comprising: a stage for placing a sample having a pattern formed on a surface; an objective lens observing the pattern; an illuminating optical system including a light source and a polarizer, selecting an arbitrary wavelength region from the light source, and epi-illuminating the sample via the polarizer and the objective lens; a detecting optical system including an analyzer having a polarization plane intersected with a polarization direction of the polarizer, detecting light from the sample via the objective lens and the analyzer, and acquiring a Fourier image of a sample surface based on the light; an imaging section imaging the Fourier image; and an analyzing section performing computation processing for determining a notable area to be affected by a state of the pattern more than other areas in the Fourier image.