The present invention relates to: a derivative in which glutamate-urea-Lysine (GUL) and isonitrile are linked by a linker; a radioisotope labeled compound comprising the derivative; and a pharmaceutical composition for treating and diagnosing prostate cancer, containing the derivative as an active ingredient. A derivative according to the present invention has high binding capacity for PSMA, which is expressed in prostate cancer, by acting as a multi-ligand through the binding of three or six derivatives to one atom of technetium or rhenium, has excellent stability in human serum when administered in vivo, and is excreted into the kidney rather than the hepatobiliary tract because of high water solubility so that a clear image of a prostate cancer tumor site can be obtained, and thus the present invention can be effectively usable as a pharmaceutical composition for treating or diagnosing prostate cancer.