1. A detection device of a planar area comprising: a planar area aligning section configured to set given areas to a plurality of obtained images, and through use of a geometric transform function that matches the area of one image of the plurality of images with the area of the other image of the plurality of images, generate a geometric transform image; and a planar area detecting section configured to detect a planar area based on the geometric transform image and the area of the other image, wherein the planar area aligning section sets a planar area detected by the planar area detecting section as the given area.