A particle composite process by using a high-speed elliptical-rotor-type mixer is analyzed. Deposition of fine particles onto the surface of core particle was selected. Rotor revolution and processing time were used as processing parameters, and the diameter of core particle was selected as powder property. The effect of these parameters on the composite process is investigated. As a result, the composite process in the mixer is classified as one of two patterns: below a critical rotor revolution, the mass fraction of fine particles deposited onto the surface of the core particle increased as the rotor revolution and the processing time increased, and then the mass fraction reached a constant value with processing time. On the other hand, in the range over the critical revolution, the mass fraction of fine particles increased at the initial processing time, and then the detachment of fine particles from the core particles occurred after a certain processing time. The critical rotor revolution was in proportin to the -0.5 th power of the core particle diameter. From these results, a model of the particle composite process in this mixer is proposed, and the composite process is explained.