A visual inspecting method for an electronic device, comprising steps of: photographing an image of a surface of the electronic device; dividing the photographed image into a plurality of unit regions and obtaining a distribution of gradation levels for each unit region; subtracting a predetermined offset value from the gradation level of the highest frequency selected from the gradation levels for each unit region so as to obtain a binarization level for each unit region; interpolating the binarization levels for unit regions so as to obtain a binarization level at each coordination position of the photographed image; and comparing the gradation level at each coordination position of the photographed image with the binarization level at each coordination position and determining that a defect is present at a coordination position where the gradation level thereat is lower than the binarization level thereat.