In the mono-component non-magnetic toner system, optimum toner charging and mass transfer are important factors to produce fine images with high quality. In previous work, we confirmed that a current flows through each system part (i.e. development roller, blade, and supply roller) during the roller rotation with toner attached on its surface. In this paper, we discuss the possible mechanism of generation of these currents in the development system. Development rollers having various surface properties were prepared for this study. It was found that the surface characteristics of the development roller considerably affected the value of the current. In particular the rate of charge decay of the roller surface strongly affected the current and also the toner charging. From these results, we propose a possible mechanism for this current generation.