1. A visual inspection method comprising: taking a photograph of an illuminated inspection target sample from above to generate an original picture; converting said original picture obtained by said taking into a binary picture; labeling said binary picture obtained by said converting to generate a labeling picture; calculating a summation of shade values of said original picture corresponding to said labeling picture generated by said labeling; and judging a pass or rejection of said inspection target sample based on said summation of the shade values obtained by said calculating.