1. An inspection area setting method for setting inspection area-defining information defining an inspection area to an image inspecting device, the image inspecting device being configured to extract a portion constituting the inspection area as an inspection area image from an original image obtained by taking an image of an inspection object, and to inspect the inspection object by analyzing the inspection area image, the inspection area setting method comprising: an acquisition step of acquiring a sample image obtained by taking an image of a sample of the inspection object; an inspection area searching step of acquiring an optimal solution of the inspection area from a plurality of candidate areas by evaluating both pixel separation and edge overlap with respect to the plurality of candidate areas that are of candidate solutions of the inspection area based on information on color or brightness of each pixel in the sample image and information on an edge comprised in the sample image, the pixel separation being a degree of separation of the color or the brightness between an inside and an outside of each candidate area, the edge overlap being an overlap degree between an contour of each candidate area and the edge in the sample image; and a setting step of setting inspection area-defining information defining a position and a shape of the contour of the inspection area obtained in the inspection area searching step to the image inspecting device.