Disclosed is a diagnostic agent which is useful for imaging the site of application at which the highest therapeutic effect is expected (i.e., the site where an HGF receptor is expressed) in the therapy of an ischemic disease with an HGF plasmid for the purpose of promoting the angiogenesis with good efficiency. The diagnostic agent is for a disease associated with a hepatocyte growth factor receptor, wherein the drug includes: a labeled product of a partial polypeptide of hepatocyte growth factor containing a heparin-binding domain； or a labeled product of a polypeptide which consisting of an amino acid sequence in which one or several amino acid residues are substituted, deleted or added to the amino acid sequence of the partial polypeptide and having a heparin-binding activity
