The present invention relates to a pattern defect inspection apparatus, wherein light emitted from an illumination source capable of outputting a plurality of wavelengths is linearly illuminated by an illuminating optical system. Diffracted or scattered light due to a circuit pattern or defect on a wafer is collected by an imaging optical system onto a line sensor and converted into a digital signal, and the defect is detected by a signal processing section. Then, the defect can be detected with high sensitivity since a surface to be formed by an optical axis of the illuminating optical system and an optical axis of the imaging optical system is almost collimated to a direction of a wiring pattern and further since an angle to be formed by the optical axis of the imaging optical system and the wafer is set to an angle with less diffracted light from the pattern. Thereby, the pattern defect inspection detecting various defects on the wafer with high sensitivity at high speed can be achieved.