Methods of fibrillation of aramid fiber for a fiber-dispersion type of composite and evaluation of the degree of fibrillation were investigated. Continuous fibrillation of aramid fiber was carried out using a vibrating ball mill. The morphology of the fiber surface was controlled by adjusting the processing time of the fiber in the mill. An index based on image analysis was proposed to represent the morphological changes of treated fiber. The interaction between powder bed and fiber was determined by measuring the force required to pull a single fiber out of a compacted powder bed. The interaction between powder and fiber increased with the degree of fibrillation.