This paper provides an overview of the recent progress of simulation technology in Japan for the development of electrophotography processes—charging, exposure, development, transfer, fusing, cleaning, and paper handling. By utilizing highly efficient hardware and software, the simulation technology has been improved significantly. Because charging, exposure, and fusing processes are based on the mechanics of continuous media, they are formulated as a set of multi-component, nonstationary, and nonlinear partial differential equations and are numerically solved by the iterative finite element method or finite differential method. In contrast, the discrete element method is used to simulate the dynamics of toner and/or carrier particles in the development, transfer, and cleaning processes. The method of direct observation with a high-speed microscope camera and particle tracking velocimetry are used to improve physical models and to confirm the adequacy of calculation results. Thus, the electrophotography processes are no longer a black box.