Disclosed is a polypeptide having a function to increase the calcium concentration in an osteoblast. Specifically disclosed is a polypeptide selected from the following polypeptides (1) to (3): (1) a polypeptide which comprises the amino acid sequence depicted in SEQ ID NO:1； (2) a polypeptide which has a function to increase the calcium concentration in an osteoblast and comprises an amino acid sequence having 60% or more sequence identity to the amino acid sequence depicted in SEQ ID NO:1； and (3) a polypeptide which has a function to increase the calcium concentration in an osteoblast and comprises an amino acid sequence produced by deleting, substituting, inserting or adding one to nine amino acid residues in the amino acid sequence depicted in SEQ ID NO:1.
