A new method to determine surface parameters of metals, viz., surface energy γ and surface diffusion coefficient Dad of metal adatoms is proposed and experimentally established. This method is based on the image analysis for the change of metal surface morphology due to electrodeposition. First, potentiostatic and galvanostatic electrodepositions are performed in the same electrolyte solution. In these experiments, average sizes of the crystal particles formed on the electrode surfaces are measured at a given deposition time. With the values obtained, computer calculations are carried out to make two kinds of Dad–γ plots corresponding to the galvanostatic and potentiostatic cases, respectively. From their intersection, the surface energy γ and the product DadC*ad of diffusion coefficient Dad and adatom concentration C*ad are determined. Each value of Dad and C*ad is easily separated by the data of C*ad measured by electrochemical technique for electrodeposition. As a result, it is found that the value of γ is kept constant at the high cathodic potentials while there is one maximum at the lower potentials, which seems to correspond to the point of zero charge (pzc) of an electrocapillary curve of mercury electrode system. The dependence of γ in the high cathodic region on the bulk concentration is also investigated. Consequently, it is concluded that surface energy γ is proportional to 3/2 power of the bulk concentration.