To provide a defect inspection device capable of detecting a microdefect in a wedge wafer part with high-throughput.

Light emitted from an upper bevel illuminating light source 3a is filtered to light with a predetermined wavelength by an upper bevel interference filter 4a, and then slit light with a width of d is illuminated to an area to be illuminated on the upper bevel of a wafer 1 by a light condenser lens 5a for an upper bevel. Irregular reflection light from the area to be illuminated of the upper bevel is transmitted through an interference filter 6a for the upper bevel having wavelength characteristics the same as those of the interference filter 4a for the upper bevel, and is condensed by a condenser lens 7a for the upper bevel and then received by a light-receiver 8a for the upper bevel such as an SPD. Specular reflection light from the area to be illuminated of the upper bevel is not entered to a receiving optical system. Thus, the light is not to be background noise.