Polarizabilities of an annular aperture in a thick conducting plane are obtained for electric and magnetic cases. The knowledge of those factors is often required in problems related to waveguide coupling and diffraction of electromagnetic waves by apertures. The polarizabilities are geometrical factors which can be found by solving static problem. In the present thesis, Hankel transform is applied to express the scattered and transmitted potentials. The problem is solved by a combination of analytic and numerical method. The resulting series solution is fast convergent and very efficient for numerical computation. The numerical calculations are performed to illustrate the behavior of polarizabilities in terms of the aperture size and conductor thickness.