Abstract: An optical mouse is operated on a work surface and includes at least one light emitter for emitting a light beam; a light receiver contained by a casing; a rolling ball arranged on the casing and opposite to the light receiver. The light beam has only one reflection by the rolling ball during an optical path thereof and then is detected by the light receiver. The rolling ball is made of transparent material and the distance thereof with the light receiver is adjustable to vary image resolution. The optical mouse can be turned over and placed on a notebook computer for using as a track ball.