A radiation detector includes a substrate, a lower electrode disposed on the substrate, a radiation detecting layer formed on the upper surface of the lower electrode, an upper electrode formed on the upper surface of the radiation detecting layer, a protection layer which is formed on the upper electrode, whose end portion extends to an end surface of the substrate and which covers the upper electrode, and a reinforcement member which is formed from the lower surface of the substrate to the surface of the protection layer and which covers the end portion of the protection layer.