A sub-micron powder of either alumina or zirconia was separated by electrophoresis. A mixed suspension of these powders was prepared at a powder concentration of 150-200 p.p.m. at pH 5.0, where both alumina and zirconia had enough positive zeta potential to prevent their heterocoagulation. A uniform and stable ascending flow of electrolytic solution at pH 7.4 was prepared, where the difference of the zeta potential between alumina and zirconia was about the maximum. The ascending flow carried a fine stream of the suspension with a diameter less than 1 mm. The fine stream of suspension was divided into two fine streams by applying an electric field of 10 V/cm perpendicular to the flow. The concentration of different kinds of particles in each separated suspension was reduced to 1/10 of that in the original mixed suspension.