A boundary-value problem of electrostatic potential penetration into two circular apertures in a thick conducting plane is solved rigorously. The scattered potentials are represented in terms of discrete and continuous modes by using the Hankel transform and superposition principle. The boundary conditions are enforced to obtain a set of simultaneous equations for the discrete modal coefficients. The electric polarizability is represented in fast convergent series which is amenable to computation. The electric polarizability is evaluated for various aperture geometries to show the characteristics of electrostatic potential penetration.