The present invention relates to a single-polarizer focused-beam ellipsometer. An ellipsometer according to the present invention includes a light source (210); a beam splitting part (220) for splitting a light generated in the light source (210) into a polarized light; an objective lens (230) for concentrately irradiating some of light split by the beam splitting part (220) onto a specimen (240); a photodetector (250) for detecting the light passed through the objective lens 230 and the beam splitting part (220) after reflected from the specimen (240) with unit cells; and a central processing unit (260) for correcting the intensity of the light detected by the photodetector (250) into a value corresponding to the unit cell of the photodetector (250) along multiple incidence plane passage of 360° with respect to respective incidence angles and processing the corrected value.