A method of three-dimensional identification of a semielliptical crack existing on the back surface of a conductive plate by direct-current electrical potential difference method with a multiple-probe sensor was proposed. The geometrical condition of the crack was specified by six parameters, the surface and inward angles of the crack plane, θsur and θin, the length and depth of the crack, c and a, and the two-dimensional location of the crack center, (yc, zc), on the back surface, respectively. Identification was carried out based on the distribution of electrical potential difference on the surface of the plate measured with a sensor composed of grid-arranged multiple probes called the "multiple-probe sensor." As an approximate cracked body and a quick analysis method were used, a number of repeated electrical potential field analyses necessary for the identification of the crack became possible within a practical time. The validity of the method was numerically confirmed by carrying out the identification based on the result by the finite element analysis.