Electro-optic sampling is a great method to detect terahertz wave, whose various EO-crystals have broad frequency response from a sub∼few THz to mid infrared. But the lack of the signal-to-noise ratio, due to weak intensity and inefficiency of the THz system, is making difficult for THz wave to be applied to practical applications. Here, the quantum enhanced EOS experiment is suggested with quantum metrology theory. By using squeezed light and homodyne detection, it is possible to increase SNR and reach Higenberg limit, which is impossible for the ordinary EOS setup which can only reach sub-shot noise limit. Proof of the theory and the experiment is introduced here.