The present invention is detection of a defect signal which is small enough to be buried in a background noise, by a method that includes detecting a defect on a specimen which is detected by another inspection device by using a detection device equipped with an optical microscope, amending positional information of the defect, observing the defect by using an SEM, wherein the detecting the defect is carried out such that forming stationary waves on the specimen by irradiating the specimen with two illumination lights having the same wavelength from the opposite directions on the same incidence plane at the same incidence angle and cause the two illuminating light to interfere; removing scattered components generated by minute irregularities on the specimen surface by a spatial filter, detecting an image formed by the scattered light not removed by the spatial filter; and processing the detected image to detect the defect.