1. An inspection apparatus, comprising: beam generation means that generates any of charged particles and electromagnetic waves as a beam; a primary optical system that irradiates an inspection object held in a working chamber with the beam; a secondary optical system that detects secondary charged particles occurring from the inspection object; and an image processing system that forms an image on the basis of the detected secondary charged particles, wherein irradiation energy of the beam is set in an energy region where mirror electrons are emitted from the inspection object as the secondary charged particles due to the beam irradiation, the secondary optical system comprises a camera for detecting the secondary charged particles, a numerical aperture whose position is adjustable along an optical axis direction and a lens that forms an image of the secondary charged particles that have passed through the numerical aperture on an image surface of the camera, and in the image processing system, the image is formed under an aperture imaging condition where the position of the numerical aperture is located on an object surface to acquire an image.