A method of preparing a radiation image conversion panel including a substrate and a phosphor layer, may include heating an evaporation source containing a phosphor raw material to evaporate the raw material and depositing an evaporated material on the substrate to form the phosphor layer, while the substrate being heated, wherein in (ii), a temperature of the substrate increases at a rate of 0 to 5.degree. C./min, and falling within a range of from 60 to 110.degree. C.