A radiation detector comprising a II-VI compound semiconductor substrate that absorbs radiation having a first energy, a II-VI compound semiconductor layer of a first conductivity type provided on a main surface of the II-VI compound semiconductor substrate, a metal layer containing at least one of a group III element and a group V element provided on the II-VI compound semiconductor layer, a IV semiconductor layer having a second conductivity type opposite to the first conductivity type provided on the metal layer, and a IV semiconductor substrate that absorbs radiation having a second energy different from the first energy provided on the IV semiconductor layer.