A precursor of a molecular probe for imaging of pancreatic islets is provided. The precursor includes a polypeptide represented by any one of the following formulae (1) to (12), or a polypeptide having a homology with the foregoing polypeptide:*-DLSKQMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (1)*-LSKQMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (2)*-SKQMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (3)*-KQMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (4)*-DLSK*QMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (5)*-LSK*QMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (6)*-SK*QMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (7)*-K*QMEEEAVRLFIEWLKNGGPSSGAPPPS-NH2 (8)DLSK*QMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (9)LSK*QMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (10)SK*QMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (11)K*QMEEEAVRLFIEWLK*NGGPSSGAPPPS-NH2 (12)