An inspecting system for security documents is disclosed, wherein a rotating cylinder provided with transparent sectors is apt to transport the document past an image acquiring device, and in which a transparency inspecting device is placed partially inside and partially outside the cylinder so that the electromagnetic inspecting beam is intercepted by the documents held lying onto the transparent sectors. Further, the inspecting system is provided with shading elements, in the optical pattern, apt to define a cone of shade only in correspondence of sensitive elements of a camera.