Polystyrene latex particles, 1.6 mum in diameter, with sulfonic acid groups were driven by the application of voltages for E < -0.4 or > 0.6 V in a well-deionized suspension, accompanied by Brownian motion. Their positions were monitored and recorded with a video-microscope at various electrode voltages. The moving rates decreased with the time of the potential application, and were proportional to the Faradaic current. Therefore, the motion is relevant to electrode reactions rather than simply the electrostatic force between the two electrodes. The electrode reactions generate OH- or H3O+. The extra charge on OH- or H3O+ is compensated by the negatively charged latex particles. From the relation between the current and the velocity of the particles, only 2% of the current contributes to the motion of the particles.