An attempt was made to determine an approximate formula for sedimentation velocity of a solid particle, when a potential difference is applied between two electrodes, from statistical analysis. The powder used was Al-modified rutil type titanium dioxide. Sedimentation velocities of this particle adsorbed by sodium metaphosphate were measured when an electric force affected this suspension. When the strength of electric field, E, affects the powder particle placed between two electrostatic charges, the equation for the sedimentation velocity of a particle can be written as : [chemical formula] where f (E, d_p) is the function concerned with an electric field, E, and particle size, d_p. This function f(E, d_p) is given as, [chemical formula] From the above equation, values of both sedimentation velocity and particle size distribution can be predicted beforehand when a powder particle exists between two electrodes.