An optical system for sensing movement is provided to improve assembly without additional installation of an aperture diaphragm by positioning the aperture diaphragm inside a wide-angle lens. In an optical system for sensing movement, an image is formed on a photo sensor by collecting light which is irradiated from a light source unit and reflected at a subject. The optical system for sensing movement includes a wide-angle lens(L) having a first lens element(LE1) and a second lens element(LE2). The first lens element has an object side surface(1) in a convex shape. The second lens element includes an object side surface(2) in a flat shape and an upper surface(3) in a flat shape. The object side surface of the second lens element is coupled to an upper surface of the first lens element.
