FLAW DETECTOR

PROBLEM TO BE SOLVED: To provide a flaw detector capable of accurately detecting the flaw of an object to be inspected without being affected by the material of the object to be inspected or disturbance such as vibration or the like. SOLUTION: The object 10 to be inspected is irradiated with inspection light from the floodlight projector of a sensor head 20 and the inspection light reflected from the object to be inspected is detected by the photodetector of the sensor head 20. The output signal of the photodetector is inputted to a low-pass filter. On the basis of the comparing result of the level of the output, signal of the photodetector, which is affected by the change of a material or disturbance such as vibration or the like, passed through the low-pass filter and a reference level, feedback control is performed so that the level of the output signal of the photodetector is stabilized. The flaw 10c of the object 10 to be inspected is detected based on the output signal of the photodetector.