A three-dimensional calculation of toner movement in a transfer region is carried out and toner scattering is simulated. This simulation includes an electric field calculation between two parallel plates and a calculation of toner movement. In order to estimate a force on a toner particle precisely, an electric field created by electrodes and surface charges, repulsive force of toner particles, mirror images of toner charges, a discharge phenomenon and toner adhesions are considered. A toner particle separates from the upper plate and begins to move downward when a transfer force overcomes the sum of the mirror force and the adhesion force. Movement of a toner particle is calculated according to Newton's motion law. From the simulation result, toner detachment happens before a discharge in a non-image region occurs. Because of the repulsive force and jumping the air gap, toner scattering happens and satellites are formed on the lower plate. In order to investigate toner scattering, a model experiment is carried out and is compared with the simulation. The number of satellites is compared between simulation and experiment, and the comparison shows good coincidence. This comparison confirms that this simulation model is useful for calculating toner movement in a transfer process. The model experiment and simulation indicates that toner scattering happens before discharges and the cause of toner scattering is mainly Coulomb's force.