According to one embodiment, a radiation detector includes a first conductive layer including a first conductive region, and a first stacked body. The first stacked body includes a first electrode separated from the first conductive region in the a direction, a first scintillator layer provided between the first conductive region and the first electrode, a first intermediate electrode provided between the first scintillator layer and the first electrode, and a first organic semiconductor layer provided between the first intermediate electrode and the first electrode.