The usefulness of a jig separator for classifying plastics in electric appliances is investigated. Although various types of jigs have been used for more than 100 years, little is still known about the precise mechanisms of jigging. Numerical simulation is conducted to obtain a better understanding of the jigging processes. The simulations give results that are very similar to those obtained by experiments. Two types of spheres with a difference in density of 10 kg/m^3 and the same diameters are classified. In addition, particles with the same settling velocity and different diameters are also classified. The jig separators found to be very sensitive to slight differences in terminal settling velocity and response time of the particles.