To provide a two-dimensional array type radiation detector which is inexpensive and precise and not affected by a centrifugal force when an X-ray CT device rotates fast.

A jig dedicated to collimator manufacture is used to fix both the ends of a channel-directional collimator plate 4 to a main support plate 1 and a support plate 2. Fix a detector fitting plate 3 is fixed to the support plate 2. Both the ends of a substrate 7 mounted with a multi-slice scintillator 5, a PDA 6, and its scanning circuit is fixed to the main support plate 1 and detector fitting plate 3 with fixing screws 10. The end of the substrate 7 is held from below with a push bolt 13 and a fixing nut 14 provided to the bottom plate 8 of a housing to fix a detector composed of the channel-directional collimator 4, multi-slice scintillator 5, and PDA 6.