A method for evaluating the distribution of electrical potential around multiple spherical defects was proposed. As the method is based on the known formulated solution for a single defect, the electric field could be analyzed efficiently in comparison with the other methods, such as the finite element method. The electric field in a conductive material with multiple spherical defects at random locations was analyzed by the method. Result of the analysis showed that the increase in the potential difference normalized by the potential difference without defects, Delta V/V-0, was in proportion to the product of the volumetric density of defects and the mean of cubed defect radius, n[r(3)](m). This universal relationship held independently of the value of n(v) and the distribution of defect radius. Using the relationship, the damage due to the multiple defects can be evaluated from the increase in potential difference.