For example, Patent Literature 1 discloses a photodiode array used in a CT (Computed Tomography) apparatus or the like. In the photodiode array of Patent Literature 1, P+-type semiconductor regions constituting a light detection region are arrayed two-dimensionally on the incident surface side of an n-type semiconductor substrate. An electrode is connected to each of the P+-type semiconductor regions. Each of the electrodes is extracted to the rear surface side on the opposite side to the incident surface through a through-hole provided corresponding to each of the P+-type semiconductor regions. The P+-type semiconductor region and the through-hole are alternately disposed in the semiconductor substrate along a predetermined direction.