This invention relates to a method of preparing a radioisotope nanostructure having a ligand-metal framework, and a radioisotope nanostructure prepared thereby. The method of preparing the radioisotope nanostructure of the invention has a simple preparation process and can thus be applied to mass production of a radioisotope nanostructure. Also, because this radioisotope nanostructure is nano-sized spherical particles and has no reactive group, it can be easily dispersed in a fluid, and this nanostructure is physically and chemically stable and thus can be utilized as a radioisotope tracer in the fields of refineries, chemistry, cement, agriculture, water resources, marine, etc. Furthermore, this nanostructure can be used for diagnosis and/or treatment in medical fields, and can be applied to checking whether a nanomaterial is harmful. In addition, this nanostructure is expected to be applicable in a variety of fields using radioisotopes.