A measurement system, comprising: a first light source that generates first light and irradiates an object with the first light, at least one of an intensity, a polarization state, and a wavelength being modulated with a first period in the first light; a second light source that generates second light, at least one of an intensity, a polarization state, and a wavelength being modulated with a second period in the second light; a first optical system that mixes light from the object based on the first light with the second light; a nonlinear optical crystal that generates third light from the mixed light by sum-frequency generation phenomenon, the third light having a frequency equivalent to a sum of a frequency of the light from the object based on the first light and a frequency of the second light; and a photodetector that measures an intensity of the third light.