Currently, the surgeries for broken bones are performed by using metallic biomaterials for early recovery. Metallic biomaterials will be continued to use as artificial bones because of high reliable mechanical properties. However, they have two deficient points; (1) they exhibit so-called stress-shielding effect due to high elasticity that induces abnormal bone absorption, and (2) they are not easily fused to living bone. In our research group, we try to develop new soft (low elasticity) titanium alloys for artificial bone by properly adjusting the microstructure. We also develop new titanium alloys that promote bone formation by controlling the behavior of osteoblast cells on the surface-treated titanium alloys.