It is desired that toners and carriers are mixed well and charged appropriately in the two-component developers of electrophotography. Further these two kinds of particles should be transported to the latent image on the photoconductive drum steadily and at a proper rate. Screw feeders are often used for this process because it is suitable for dealing with mixing, charging and transporting simultaneously. Unfortunately, it is very difficult to know experimentally details of dynamic behavior of particles affected by complicated geometric conditions in the developers unit. As a method for calculating particle motion, DEM (Discrete Element Method) has been attracting a great attention in various fields related to powder and particles. In DEM motion of individual particles is calculated by using the Newton's equations of motion. DEM was applied in this work to study motion of carriers in a screw feeder. The properties concerning mixing and transporting particles were analyzed.