Disclosed are a radiation scintillator and a radiation image detector comprising the radiation scintillator. The radiation scintillator which exhibits enhanced sharpness and luminance and is excellent in shock resistance, comprises, on the substrate, a scintillator layer containing a phosphor and formed by a process of gas phase deposition, and the scintillator layer exhibits a thickness of 100 to 500 μm, a filling factor of the phosphor of 75 to 90% by mass and a layer thickness distribution of not more than 20%.