An ellipsometer is provided. The ellipsometer includes: a polarizing optical element, comprising a prism, that is configured to split reflected light into two linearly polarized components of light having polarization directions orthogonal to each other, the reflected light generated by reflecting illuminated light, including linearly polarized light that is polarized in one direction, from a measurement surface of a sample; an interference member, comprising at least one body, that is configured to form at least one interference fringe in which the two linearly polarized components of light interfere with each other in directions different from the polarization directions; an image detector configured to detect the at least one interference fringe; and an analysis device including at least one processor, the analysis device configured to calculate ellipsometry coefficients Ψ and Δ based on the at least one interference fringe that is detected.