| abstract |
(57) [Problem] To provide a crystal grain size measuring method and apparatus capable of accurately measuring a crystal grain size even when the difference in density from spangles and other crystal grains is small. SOLUTION: Light emitted from a light source 2 to a surface to be measured 11 is reflected only by spangles existing in the surface to be measured 11, an image pickup device 3 is provided in the reflection direction, and an image is taken. The particle size of the spangle is measured by calculating the particle size using the image processing device 4. |