A radiation detector that includes a flexible substrate, a plurality of pixels that are provided on the substrate and each include a photoelectric conversion element, a scintillator that is laminated on the substrate and includes a plurality of columnar crystals, and a flexure suppression member that suppresses flexure of the substrate. When L is the average height of the columnar crystals, r is the average radius of the columnar crystals, d is the average distance between the columnar crystals, [Phi] is the average angle of tip parts of the columnar crystals, and R is the radius of curvature of flexure of the substrate caused by the weight of the scintillator, the rigidity of the flexure suppression member satisfies R ≥ L-r/tan[Phi]+4r.{(L-r/tan[Phi])2-(d/2)2}1/2/d.放射線檢測器包括：具有可撓性的基板；設置於基板且分別包含光電轉換元件的多個像素；具有層疊在基板上的多個柱狀晶體的閃爍體；以及抑制基板的撓曲的撓曲抑制構件。在將柱狀晶體的高度的平均值設為L、將柱狀晶體的半徑的平均值設為r、將柱狀晶體彼此的間隔的平均值設為d、將柱狀晶體的前端部的角度的平均值設為Φ、將由於閃爍體的重量而在基板上產生的撓曲的曲率半徑設為R時，撓曲抑制構件具有滿足R≥L-r/tanΦ+4r・｛（L-r/tanΦ）2-（d/2）2｝1/2/d的剛性。
