The composite process of deposition of fine particles onto the surface of core particles by a high-speed elliptical-rotor-type mixer is analyzed. In this paper, the effect of fine particle size on the composite process is investigated. Soda-lime glass beads were selected as core particles, and three kinds of titanium dioxide were used as fine particles. The mass fraction of fine particles fixed on the surface of the core particles was measured with a wet sieve technique, and the coated layer of fine particles was observed by a scanning electron microscope. As a result, the mass fraction of fine particles deposited onto the surface of the core particle increases as the rotor revolution and the processing time increase regardless of fine particle size. However, the detachment of fine particles from the core particles occurs after a certain processing time regardless of fine particle size. The critical revolution decreases as the fine particle size increases. Below the critical revolution, the mass fraction of fine particles increases as the fine particle size decreases. These results are explained by considering the mechanics of powder beds.