Abstract: A template defect inspection method using an optical system includes emitting linearly polarized light to a template having a metal film formed on at least part of a concave-convex structure that is formed on a substrate and that has a line-and-space pattern, acquiring information on a polarization-rotated component, which is different from linearly polarized light incident on the template, of light reflected by the template in accordance with the emission thereto, converting the acquired information on the polarization-rotated component into an electrical signal, and processing the electrical signal.