Abstract: In the conventional technology for edge detection by normalizing brightness value of a target pixel C for edge determination and brightness of peripheral blocks of the target pixel C, an effect on an image due to a camera lens has not been considered. Specifically, the camera lens has a circular shape and the photographed image is basically formed by circularly collected light. In the conventional technology, however, it has been difficult to carry out high-precision edge detection due to rectangular shape of the peripheral blocks. In order to solve the above deficiency, in an aspect of the present invention provides an edge detection apparatus having a function of weighting the pixel values in the ‘peripheral area’ to be compared with the target pixel C for edge determination, such that the peripheral area has the circular shape.