An apparatus for measuring a refracting power of an optical system which comprises: a beam projecting optical system which projects a predetermined moving luminous flux to an optical system to be inspected; a beam condensing optical system in which a photoelectric conversion element receives a luminous flux transmitted through the optical system to be inspected; and a processing system which obtains the refracting power of the optical system to be inspected, based on an output from the beam condensing optical system; wherein a rotating plate having at least one tooth of a converging shape, which is protruded outwardly from a center of the rotating plate, is disposed in a beam path of the beam projecting system; and a luminous flux, both edges, in a moving direction thereof, of which are inclined to the moving direction with angles being different with each other and correspond to both sides of the tooth, irradiates the optical system to be inspected, by intermittently blocking the beam path by the tooth.