PURPOSE: To provide a rotation-type flaw inspection apparatus wherein flaw on the surface of a substrate on which a circuit pattern or the like has been formed is inspected by using a simple signal processing system and at a high speed.

CONSTITUTION: A luminous flux from a light source 26 is cast on a point P, to be inspected, on a wafer 1. A luminous flux 32 from the point P to be inspected forms, on a rear-side focal-point face 33 via a Fourier transform lens 31, the Fourier transform spectrum of a circuit pattern on the point P to be inspected. A luminous flux which has removed a Fourier transform spectrum not containing any error from the Fourier transform spectrum by a spatial filter 34, is received by a photoelectric conversion element 41. While the wafer 1 is being turned by a turntable 21 and moved in y-direction, the spatial filter 34 is turned in synchronization with the wafer 1.