The development of the Co-free materials with high erosion resistance is anticipated for the equipment parts in power plants. The erosion resistance against the impact of hot water jets onto the specimen surface was experimentally investigated for the Ti-Ni shape memory alloys (SMA), as compared with that of an existing Co-based alloy (Stellite). In total, the erosion resistance of Ti-Ni SMAs is superior to that of Stellite. The essential erosion-damage mechanism of Ti-Ni SMAs is the cavitation, and that of Sellite is the combination of the shearing stress and the cavitation. It is suggested that the Ti-Ni SMA will be the promising alternative materials of Stellite.