Abstract: The present invention relates to a biodegradable carrier for carrying a radioisotope, which is formed from at least one biodegradable polymer selected from the group consisting of poly(lactic-co-glycolic acid) (PLGA), poly(lactic acid) (PLA), poly(?-caprolactone) (PCL), chitosan, poly(?-glutamic acid) (PGA), and polyethylene glycol (PE) in which its hydroxyl group is substituted with an amino group and grafted with tetraazocyclododecanetetraacetic acid monosuccinimide ester (DOTA-NHS), in which nitrogen atoms contained in the DOTA-NHS are provided for coordinating with a radioisotope. The present invention also relates to a kit which includes a first container containing the biodegradable carrier for carrying a radioisotope according to the present invention and a second container containing a radioisotope.