In spectral detection for detecting the shape of repeating pattern structures uniformly formed on a surface of a test object, it is advantageous to use light having a wide wavelength range in a short wavelength region. However, it is not easy to realize a relatively simple optical system capable of spectral detection of light having a wide wavelength range in a short wavelength region, namely in ultraviolet region. The present invention provides an inspection apparatus for detecting pattern defects. The inspection apparatus includes a spectral detection optical system capable of spectral detection of light in a wavelength range from deep ultraviolet to near infrared. The spectral detection optical system includes a spatially partial mirror serving as a half mirror and a reflecting objective provided with an aperture stop for limiting the angle and direction of light to be applied to and reflected by a test object.