Ice crystal icing occurs in the compressors of jet engines at a static mainstream temperature of approximately 30 ℃. Therefore, it is important to consider the melting of the ice crystals (i.e., state change) because ice crystals fly in a high-temperature environment. In this study, to accurately clarify how ice crystals impinge on a rotor blade, we conducted a trajectory simulation considering the state change of ice crystals flying around the rotor blade of an axial fan. The ice crystal trajectories were tracked using a Lagrangian approach with a one-way coupling. The state change of the ice crystals was evaluated from the energy balance of the heat received from the surrounding fluid, the heat passing through the ice crystals through heat conduction, and the heat of the evaporation or condensation on the surface. The results show that the longer the ice crystals fly, the more they are affected by the phase transition, which becomes more remarkable as the sizes of the ice crystals decrease. In addition, the water content of ice crystals impinging near the tip side is particularly high in the entire rotor blade.