A radiation image conversion panel is disclosed exhibiting superior homogeneity of an activator in a phosphor layer and enhanced luminance and improved sharpness, comprising on a support at least one phosphor layer, wherein the phosphor layer comprises a stimulable phosphor and is formed by a vapor deposition process so that the phosphor layer has a layer thickness of 50 m to 1 mm, and the phosphor layer exhibits a pH between 0 and 7. There is also disclosed a preparation method of the radiation image conversion panel.