Disclosed are a radiation image conversion panel which has achieved a radiation image with enhanced sharpness and improved moisture resistance and shock resistance, and a production method thereof. The radiation image conversion panel comprises, on a support, a phosphor layer comprising phosphor columnar crystals, each composed mainly of cesium iodide (CsI) and formed by a process of gas phase deposition, wherein a coefficient of variation of crystal diameter of the phosphor columnar crystals is not more than 50% and a coefficient of variation of phosphor filling factor of the phosphor layer is not more than 20%.