The present invention provides a radiation detector UBM electrode structure body and a radiation detector which suppress the degradation of metal electrode layers at the time of formation of UBM layers and achieve sufficient electric characteristics, and a method of manufacturing the same. A radiation detector UBM electrode structure body according to the present invention includes a substrate made of CdTe or CdZnTe, comprising a Pt or Au electrode layer formed on the substrate by electroless plating, an Ni layer formed on the Pt or Au electrode layer by sputtering, and an Au layer formed on the Ni layer by sputtering.