The measurement system comprises a holder for holding a dielectric film formed on at least a semiconductive substrate and sandwiched between the substrate and a conductive film, voltage application terminals for applying voltage between the substrate and the conductive film, variable voltage source for supplying the voltage to the voltage application terminals, a light source for irradiating the dielectric film with light including wavelength of an infrared region and transmitting the light through the dielectric film, light absorbance detector receiving the light transmitted through the dielectric film, for detecting absorbance of an absorbed light component in an absorption wavelength region intrinsic to the dielectric film, and a potential difference measurement unit for measuring a potential difference between the substrate and the conductive film of the dielectric film on the basis of change in absorbance of the light component when the voltage is changed by the variable voltage source.