An evaluating apparatus uniquely determines a twist angle, a cell gap and a mean tilt angle through a method, in which a linearly polarized light beam is firstly radiated to a sample of liquid crystal display element so as to produce a transmitted light beam, subsequently, a photo-multiplier measures at least one of a directional dependency of a polarization of the transmitted light beam and a wavelength dependency of the polarization of the transmitted light beam and, finally, a computer system determines the twist angle, the mean tilt angle the cell gap on the basis of the directional dependency or the wavelength dependency.