A method for inspecting a defect of a surface of a sample includes irradiating a laser beam on the sample surface a plurality of times so that at least part of an illumination field of the laser beam on the sample surface illuminates a first area of the sample surface each of the plurality of times, detecting a plurality of scattered light rays from the first area caused by the plurality of times of irradiations, correcting errors of detection timings for the plurality of detected scattered light rays, correcting at least one of adding and averaging the plurality of scattered light rays, determining a defect on the sample surface based on a calculation result in accordance with the at least one of the adding and averaging.