A flat panel radiation detector is disclosed, comprising a scintillator panel provided on a support with a phosphor layer comprising columnar crystals and a protective layer sequentially in this order, and the scintillator panel being coupled with a planar light receiving element having plural picture elements which are arranged two-dimensionally, in which the difference between to average void fraction of an edge portion of the phosphor layer and the average void fraction of a base portion is not less than 5% and not more than 25%, and the void fraction decreases from the base portion to the edge portion. There is provided a flat panel radiation detector with a phosphor layer which exhibits enhanced physical resistance to shock and is superior in sharpness and emission efficiency.