Bone formation by osteoblast may be closely related to the increase in intracellular Ca²⁺ activity of osteoblast. In order to study the effects of changes in Ca²⁺ activity of osteoblast-like cell on fracture healing, we changed intracellular Ca²⁺ activity of osteoblast-like cells by vanadate and verapamil. And the process of fracture healing was observed after injection of the treatment osteoblast-like cells into the fracture site by hematoxylin-eosin (H-E) stain and bromodeoxyuridine (BrdU) stain. The results were as follow: 1) The most effective range of concentration which could facilitate bone formation was 10-6 to 10-5 M. 2) H-E stain showed more abundant osteoblast and osteoid tissues, more active mitotic division of osteoblast, and earlier appearance of chondroblast and chondroid tissue, making the maturation of woven bone faster in the vanadate-treated group than in the control group. The opposite was true in the verapamil-treated group compared with the control group. 3) BrdU labeling index showed more active osteoblastic proliferation in the vanadate-treated than in the control group. The opposite was observed in the verapamil-treated group compared with the control group. From these results, the fracture healing appears to be facilitated and decelerated by vanadate which apparently increase intracellular Ca²⁺ activity of osteoblast and verapamil which decreases it, repectively. Therefore the change of intracellular Ca²⁺ activity of osteoblast can be considered to be one of fracture healing mechanisms and expected to be applied for clinical purpose.