A collimator, which is adhesively bonded to a detector element array, is prevented from falling off from the radiation detection apparatus even in case that a failure of the adhesive joint occurs in the collimator. There is provided a radiation detection apparatus comprising: a detector element array in which a plurality of detector elements are arranged substantially in a fan-angle direction and in a cone-angle direction of a radiation； a collimator adhesively bonded to a side of the detector element array on which the radiation impinges, and having outer end surfaces on both sides in the slice direction tapered to align with a direction of emission from a radiation source； and a pair of blocks disposed to sandwich the collimator in the cone-angle direction, and having inner end surfaces on both sides in the cone-angle direction tapered to align with the direction of emission.
