To accurately detect a defect on the surface of a sample at all times, even when the sample partly has a transparent part.

This device irradiates light to a sample surface 24 and reflected light from the sample surface 24 is obtained via an observation system including a CCD camera 32 for image processing, thereby detecting a defect on the sample surface 24. In this case, the device has a holder 28 of hollow structure over such an area as corresponding to a sample except a holding part to retain the sample around the reverse side thereof at the position of the sample surface 24, and a reflection preventive board 34 laid at the opposite side of the observation system via the holder 28 and outside the range of the depth of focus of the observation system.