Ground surface potential distribution generated by current injection was studied to estimate the shape of buried bodies. Since the uniform ground system including a homogeneous buried body is perfectly determined with the surface shape of a buried body and resistivities in/around a buried body, inversion is easy if the surface shape is described with some parameters. N electrodes are arranged in 2-D grid manner on the ground, and two electrodes among them are used for current injection, while the others for measurement of potentials. M times of measurements are repeated while changing combination of electrodes for current injection. The potential distribution measured by the mth electrode pair is represented by N-2 dimensional vectors. The square error between this distribution and calculated one is the function of k parameters on the surface shape and resistivities on a buried body. Both shape and resistivities can be estimated by solving an optimum value problem using the square error as evaluation function. Analysis is easy for a spherical body with 6 unknown parameters, however, it is difficult for more complex bodies than elliptical one or more than two bodies. 5 refs., 9 figs.