A defect inspection device has: an illumination optical system which irradiates a predetermined region of an inspection target with illumination light; a detection optical system which has a detector provided with a plurality of pixels by which scattered light from the predetermined region of the inspection target due to illumination light from the illumination optical system can be detected; and a signal processing portion which is provided with a correction portion which corrects pixel displacement caused by change in a direction perpendicular to a surface of the inspection target with respect to a detection signal based on the scattered light detected by the detector of the detection optical system, and a defect determination portion which determines a defect on the surface of the inspection target based on the detection signal corrected by the correction portion.