The problem of diffraction of a normally incident plane wave at a hollow wedge formed by two different semi-infinite planar impedance sheets is studied numerically by using the parabolic equation (PE) method. It is assumed that either the electric or the magnetic field is parallel to the edge of the wedge. After having proved the uniqueness of the solution of the parabolic equation for passive wedge faces, the PE is solved via Crank-Nicolson finite difference scheme. A good agreement between the PE numerical results and available results for specific cases has been shown. In addition, the diffraction behavior dependent upon the parameters of the wedge faces has been displayed by several examples.