In this study, temperature-sensitive magnetic particles were microencapsulated with fluorescent dyes to create a multifunctional working fluid. In this experiment, the microcapsule particles obtained from the in-liquid drying method were dispersed in water together with a surfactant, flowed through a visualization channel provided with a magnetic field, and the flow phase was observed. The visualization channel is made of cycloolefin polymer. An observation unit was provided in the center of the flow path, and the excitation light was irradiated to excite the fluorescent dye encapsulated in the microcapsules, and the fluorescent transmitted through the two types of filters was observed. When a magnetic field was applied, clusters were formed in the channel. This cluster grew over time. At the same time, the process of cluster migration and growth were observed near the wall surface. Furthermore, the experiment was conducted by changing the flow velocity and magnetic flux density. As a result, the cluster length decreased monotonically due to the increase in the flow velocity and the decrease in the magnetic flux density in the magnetic field supply section. In addition, by heating the flow path, the magnetization of the temperature-sensitive magnetic particles in the microcapsules was also reduced, and cluster formation was suppressed.