Three-dimensional (3-D) resistivity inversion including a topographic effect can be considered theoretically to be the technique of acquiring the most accurate image in the interpretation of resistivity data, because it includes characteristic image that the actual subsurface structure is 3-D. In this study, a finite-element method was used as the numerical method in modeling, and the efficiency of Jacobian calculation has been maximized with sensitivity analysis for the destination block in inversion process. Also, during the iterative inversion, the resolution of inversion can be improved with the method of selecting the optimal value of Lagrange multiplier yielding minimum RMS(root mean square) error in the parabolic equation. In this paper, we present synthetic examples to compare the difference between the case which has the toprographic effect and the other case which has not the effect in the inversion process.