A method and apparatus enabling the placement of a mark on a lens at a desired position, easily and rapidly, without damaging the lens. The method comprising (1) the step of measuring a lens in which the optical properties and the reference position of the spectacle lens are measured and (2) the step of processing in which the lens is processed based on the optical information obtained in the step of measuring a lens. In the step of measuring a lens, the optical properties of the lens, such as the prism value, are measured using a desirable position selected as on the uncut lens as the position of measurement. An an optical reference position, such as the optical center, is calculated, a guiding mark is placed at the calculated position the relationship between the mark and the optical reference position is used in subsequent cut processing.