When the intensity of scattering light from a defect on a sample becomes very low according to the diameter of the defect, the dark noise from a sensor device itself accounts which a large proportion of the detected signal outputted from the sensor and thus it is difficult to detect minute defects. Furthermore, since a laser light source is pulsed into oscillation, pulse components from the laser light source are superimposed on the detected signal outputted from the sensor, and therefore it is difficult to detect defects with high accuracy. The present invention is a defect inspection device having irradiation means which producing pulsed operation and irradiating a surface of a sample with a laser beam, detection means which detecting scattering light generated at the surface of the sample in response to the irradiation provided by the irradiation means, and a processing portion which generating a delay signal based on the laser beam emitted by the irradiation means and processing the scattering light detected by the detection means using the delay signal.