Computer simulation of sieving behavior of powders was performed to estimate the sieving rate by the particle element method. The simulated time-residue curve of sieving agreed well with the experimental curve. Furthermore, the simulation can well represent the sieving behavior of cohesive powders. On the basis of the simulation results, the equation to estimate the sieving rate was proposed. The equation involves three engineering parameters newly defined in this study. The relationship between the engineering and operating parameters in the sieving, such as the vibration amplitude and frequency of the sieving surface, is obtained by the simulation. The applicability of the proposed equation is confirmed by experimental sieving of silica sand.