An irregularity defect inspection apparatus for inspecting an object to be inspected having a repeated pattern composed of regularly arranged unit patterns on the surface thereon to detect an irregularity defect occurring in the repeated pattern. The apparatus includes a light source apparatus having a light source for applying light to a region including an inspection region of the object to be inspected at a desired incidence angle, and an observation apparatus having a light-receiving optical system for receiving light which is generated from the inspection surface of the object to be inspected perpendicularly thereto when light is applied by the light source apparatus. The light source apparatus is provide with a light source having a parallelism of 2 degrees or less and an illuminance of 300000 Lx or higher.