An ellipsometry system and a detection unit thereof are capable of achieving miniaturization and price reduction associated therewith. The ellipsometry system includes the detection unit that: has an optical polarization element; separates an interference polarization beam obtained by causing the object-reflected polarization beam and reference reflected polarization beam to interfere with each other into a plurality of interference polarization beams on a wavelength basis; and detects the respective separated polarization components in each wavelength. The optical polarization element: has a birefringence characteristic including a first refractive index and a second refractive index; receives the separated interference polarization beams of the respective wavelengths in a wavelength order and in a parallel manner; separates the separated interference polarization beam of each wavelength, on a polarization component basis, while transmitting the same, and outputs the respective separated polarization components in each wavelength in the same direction but along different optical axes.