PURPOSE: To have accurate and certain inspection including chromatic unevenness free from projections/recesses by determining the adaptivity factor of the concentration histogram of the photographed image data to the normal distribution of that of many articles of acceptable goods, and using the bottom as a threshold when its frequency distribution is bimodal distribution.

CONSTITUTION: A concentration histogram is determined for the image data photographed by a photographing device, and determination of the adaptivity factor is made corresponding to the difference between the concentration histogram at this time and the theoretical frequency conforming to the normal distribution having respective means of standard deviation and the mean of each concentration histogram which has been determined from many individual samples of acceptable goods. This calculative motion to determine the adaptivity factor is made each time image data is fed to obtain number of adaptivity factors, and if its frequency distribution is bimodal distribution, examination is made by using its bottom as a threshold, and if not, examination is made by comparing the mean of the variable distribution with a preset threshold. Thereby the surface state including chromatic unevenness, etc., free from projections/recesses is sensed with a sense near the human senses.