1. An edge detection apparatus, comprising: an acquisition unit for pixel value of target pixel, acquiring a pixel value of a target pixel for edge determination; a calculation unit for blurring average pixel value, calculating a blurring average pixel value that is an average value of pixel values in an area peripheral to the target pixel for edge determination; and a determination unit, determining whether the target pixel value divided by the blurring average pixel value is more than or equal to a predetermined threshold value, wherein the calculation unit for blurring average pixel value further comprises a weighting section, upon calculating the average value, weighting the pixel values of the peripheral pixels, such that the peripheral area becomes equivalent to a circular area having the target pixel for edge determination as an approximately central point.