A method and device for measuring a voltage (V, Vn) between two terminals (la, lb), in particular an AC voltage in the high-voltage regime, is disclosed. The method and/or device relies on an electro-optic effect in an electro-optical element (2; 2a, 2b, 2c). This electro-optic effect introduces, e.g., a different optical phase shift in two perpendicularly polarized light waves that travel through the electro-optical element (2; 2a, 2b, 2c). Thus, a signal indicative (Sn) of the electric field at the position or over the length of the n-th electro-optical element (2; 2a, 2b, 2c) can be measured. According to the invention, ambiguities in the signals (Sn) are resolved by using a hypthesis test on an additional reference signal or quadrature signal (Sn'). By arranging a plurality of these electro-optical elements in series between the terminals, advantages in terms of cost efficiency and insulation are achieved. Furthermore, a device for measuring a high-voltage is disclosed.