1. A circuit pattern inspecting apparatus, which detects secondary electrons or back scattering electrons generated by irradiating an electron beam on a substrate having a circuit pattern formed thereon and detects an abnormality of said circuit pattern, comprising: an image processing unit for generating an image based on an intensity of a signal of said detected secondary electrons or back scattering electrons and causing said image to be displayed on a display section of an interface; and a control unit for performing a frequency analysis of a noise contained in said image.