According to an embodiment, a photodetector includes a photo detection layer, light conversion members, and a first member. The photo detection layer includes, on a light incident surface, plural pixel regions and a surrounding region. The pixel region holds a photo detection element to detect the light. The surrounding region is a region other than the pixel regions on the light incident surface. The light conversion members are arranged to oppose the pixel regions in the photo detection layer and convert radiation to the light. Each light conversion member includes a bottom surface opposing the pixel region in the photo detection layer, a top surface opposing the bottom surface, and a lateral surface connecting the bottom and top surfaces. The first member is disposed on a portion of the surrounding region on the light incident surface and covers a portion of the lateral surface of the light conversion member.
