METAL DEFECT DETECTION METHOD

PROBLEM TO BE SOLVED: To provide a metal defect detection method capable of highlighting defect through etching treatment of the inspection surface of a metal sample, while when detection of the defect is carried out by imaging the inspection surface with an imaging device, brightness of non-defect parts on the imagery of inspection surface is made to be homogenized and brightened, leading clear defection of defect part.SOLUTION: An inspection surface 2 of a metal sample 1 is polished unidirectionally, by etching treatment of the metal sample 1, defect in metal material is highlighted, linearly continuous light sources or a light source (a linear light source 4) a plurality of point light source arranged linearly are used as irradiating light source, a linearly direction 17 of the linear light source 4 and the polished direction 11 are presumed to be a same direction, the inspection surface 2 is irradiated by the linear light source 4 from a perpendicular direction to the polished direction 11, and the inspection surface 2 is imaged by an imaging device 3. Thereby, brightness of the non-defect parts in the inspection imaged imageries is to be homogenized and brightened, making the defect part 6 to be detectable clearly.