This study has conducted a small model experiment to visualize erosion process of granular subbase course material due to pavement pumping. The experiment requires video processing technology that automatically tracks the movement of the subbase course material at the particle level. Therefore, this study developed a method to track the particles during the pumping experiments using fluorescent paint-dyed particles and a black light. The experimental results showed that the paint-dyed particles showed sufficient luminance in the video, and that automatic tracking was possible. In the pumping model experiment, it was found that dyed particles just below the joints showed significant settlement behavior in the early stage of wheel-loading, and that the settlement converged as the number of cycles of loading increased. Furthermore, it was confirmed that the horizontal trajectory of the particles moved in the direction of the joints.