An object is to prevent occurrence of an insensitive zone to radiation in parallel arrangement of multiple units. This radiation detecting unit 1 is provided with a PD array 5 including a plurality of PD elements 13 arrayed opposite to a scintillator 3 and output electrode pads 23 arrayed corresponding to the PD elements 13, integrated circuits 7 for processing signals from the PD elements 13, a flexible substrate 9 for mounting of the PD array 5 and integrated circuits 7, and a radiation shield plate 1 provided opposite to the PD array 5 with the flexible substrate 9 in between and formed so that ends thereof 11a are located inside the PD array 5； the output electrode pads 23 have an array pitch made shorter than that of PD elements 13； the flexible substrate 9 is folded along the ends 11a at intermediate regions A 3 between mounting regions of the PD array 5 and integrated circuits 7, whereby the integrated circuits 7 are arranged on the opposite side to the PD elements 13 with the radiation shield plate 11 in between.
