The present invention provides a clinically usable radiolabeled compound that is precisely directable in vivo to a target tissue. The compound of the present invention has a first polypeptide or an analogue thereof, and a second polypeptide bonded to an N-terminus of the first polypeptide or the analogue thereof. In the compound, the first polypeptide is a polypeptide that specifically binds with a protein expressed in a target tissue, the second polypeptide has an amino acid region that has a high affinity for a radioactive metal nuclide, and the radioactive metal nuclide that has a high affinity for the amino acid region is held in the amino acid region.
