PROBLEM TO BE SOLVED: To provide a defect inspection method with which a minute defect can be detected and the dimension of the detected defect can be measured with high accuracy, and to provide a weak light detection method and a weak light detector.SOLUTION: A defect inspection method includes: an illumination light adjustment step for adjusting light emitted from a light source 2; an illumination intensity distribution control step for forming light flux obtained by the illumination light adjustment step into desired illumination intensity distribution; a sample scanning step for displacing a sample W in a direction substantially perpendicular to a longitudinal direction of the illumination intensity distribution; a scattered light detection step for counting the number of photons of scattered light emitted from a plurality of sub regions within a region irradiated with illumination light, and outputting a plurality of corresponding scattered light detection signals; a defect determination step for process
