A pancreatic endocrine cell indicating agent of the present invention includes a modified polypeptide in which a metal chelator binds only to an amino acid that is located at a site other than a somatostatin receptor-binding active site in a polypeptide selected from the group consisting of somatostatin and somatostatin analogs and a radioactive metal nuclide held by the metal chelator. According to the present invention, it is therefore possible to provide a novel pancreatic endocrine cell indicating agent.
