He ion bombardment behaviors of Mo-0.5V alloy scavenged by addition of 0.2wt% Sc was investigated by hardness measurement and transmission electron microscopy. The ion bombardment was carried out at two temperatures, 373K with 50MeV He ions and 1073K with 10MeV He ions. He ion bombardment-induced hardening was increased with increasing fluence in the range of 5.0×10^(20) to 1.8×10^(21) He^(++)/㎡ in the both of hardness plateau region and hardness peak region. No cavity was observed in the specimen bombarded at 1073K to a fluence of 1.2×10^(21) He^+/㎡, however a number of cavities were observed in the specimen post-bombardment annealed at 1473K for 1 hour.)