Based on transformation-optical approach, the distribution of permittivity and permeability for the elliptical concentrator is derived and functionality of the concentrator is numerically confirmed by the finite element solver COMSOL. The influence of the focus area and deviation of material parameters from perfect elliptical concentrator on the concentrating effect is studied. Results show that the smaller the focus area is, the stronger the total energy density is achieved; the performance of the concentrator is independent on loss tangent when it is less than or equal to 0.01. Besides, for the circular concentrator, the results in this paper are compared with the results of Rahm and validity of the proposed model is proven.