PURPOSE: To judge the surface condition of a material surely in a narrow space as well, by changing the scanning periods of a flash irradiating means and a photoelectric converter, discriminating two kinds of light information and performing temp. measurement and abnormality detection with the same camera.

CONSTITUTION: A photoelectric conversion camera 3 which is sensible in an IR region as well is provided so as to aim the surface of a high-temp. material 2 which is conveyed with a conveying roll 1. A periodic flash illuminating lamp 4 which emits illuminating light toward the detecting part on the surface of the material 2 is disposed. The light made incident through a lens 3a to the camera 3 is converted photoelectrically with a line sensor, and an electric signal is inputted to a signal processing device 5. The result of processing is displayed on a display 6. The photoelectric converter outputs the integration value of the light incident thereto during the scanning period set with a camera controller 7 to the unit 5. Detection of flaw is accomplished when the scanning period is short and measurement of temp. is accomplished when the period is long. The entire surface of the material 2 is judged by changing the scanning period alternately as mentioned above.