A three-dimensional contour scanning device including an image sensing element, a light source and a single polarity element is provided. The light source is used for emitting a projection light to a to-be-scanned object through a projection optical path. The projection light reflected from the to-be-scanned object becomes an imaging light further reflected to the image sensing element through an image-formed optical path. The single polarity element is disposed on the projection optical path and the image-formed optical path.