Disclosed is a defect inspection device wherein laser light is outputted from an output unit (3), and a spot of the laser light is formed on a main surface (91) of a substrate (9). The laser light spot is moved on the main surface (91) by means of a spot moving mechanism (5). In a light receiving unit (4), when the laser light spot passes the position of a defect on the main surface (91), scattering light from the spot is received, and intensity of the scattering light is acquired. In an atmosphere adjustment unit (6), oxygen concentration or oxygen quantity at least in the vicinity of the laser light spot is reduced more than that in the surrounding air. Consequently, growth of particles on the main surface (91) due to laser light irradiation can be suppressed.
