To provide a molecular probe for imaging of pancreatic islets. A molecular probe for use in imaging of pancreatic islets is provided. The molecular probe includes any one of the following polypeptides: polypeptides represented by the following formulae (1), (5), and (9); and polypeptides having homology with the foregoing polypeptides: Z-DLSXQMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (1) Z-DLSKQMEEEAVRLFIEWLXNGGPSSGAPPPS-NH2 (5) B-DLSKQMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (9) where X in the formulae (1) and (5) and B- in the formula (9) indicate that an amino group is labeled with a group represented by the formula (I) below having an aromatic ring, wherein A represents either an aromatic hydrocarbon group or an aromatic heterocyclic group, R1 represents a substituent that contains radioactive iodine, R2 represents either a hydrogen atom or a substituent different from that represented by R1, and R3 represents any one of a bond, a methylene group, and an oxymethylene group.