To provide a Mueller matrix microscopic ellipsometer capable of measuring the Mueller matrix of a sample if either one of an irradiation optical system side and a detection optical system side includes an active element.

An incident optical system 7 has a first lens system 11 for guiding parallel light to an object lens 1 and an active polarization element group 12 for independently controlling at least two elements of a first, a second and a third elements of a Stokes vector of the parallel light. An emission optical system 8 has a polarization element group and a second lens system 14 for forming an image of the image formed on a rear side focal plane 4 of the object lens 1 on a two-dimentional detector 9. The two-dimentional detector 9 images a plurality of images on the rear side focal plane 4 at a plurality of settings of the active polarization element group 12. A calculation device 15 calculates at least three elements of the vector indicating optical effects from the object lens 1 to the two-dimentional detector 9 on the basis of the plurality of images. The calculation device 15 calculates at least nine elements of the Mueller matrix of a sample 10 on the basis of an image corresponding to each of the elements of the vector.