Disclosed herein is a method for the preparation of radioisotope-labeled compounds using CNT. It comprises filling the carbon nanotube with a radioisotope; and labeling a physiologically active material with the radioisotope charged in the carbon nanotube. Taking advantage of CNT, the method can prepare a radioisotope-labeled compound invention at a high yield and in a simple manner. Also, the radioisotope, when remaining unreacted, can be recovered by the filtration of the CNT, thereby achieving the prevention of radioactive contamination and the reduction of radioactive waste. Further, the radioisotope-labeled compound is useful as a contrast medium for imaging the hepatobiliary system.