In a dielectric constant measuring apparatus provided are a light source for irradiating a substrate with light in a visible or near-ultraviolet wavelength range, a spectroscope for receiving reflected light from the substrate, and a first optical characteristic acquiring unit for acquiring the spectral reflectance of the substrate. Further are provided therein a light source for irradiating the substrate with light in an infrared wavelength range, a spectroscope for receiving transmission light from the substrate, and a second optical characteristic acquiring unit for acquiring the spectral transmittance of the substrate. The dielectric constant of a dielectric film on the substrate is obtained by a first parameter set calculation unit, a second parameter set calculation unit and a dielectric constant calculation unit, using the spectral reflectance and spectral transmittance of the substrate. It is thereby possible to achieve a noncontact measurement of the dielectric constant of the dielectric film on the substrate.