The present invention relates to a radiation image converting panel with a structure to realize an improvement in moisture resistance in the periphery of the panel. The radiation image converting panel comprises a support body and a radiation converting film formed on the support body. The radiation converting film is formed on a film forming region which exists within a first main surface of the support body and includes at least a gravity center position of the first main surface. An average crystal diameter of columnar crystals located on a peripheral measuring area of the film forming region is controlled to be 1.3 times or more larger than an average crystal diameter of columnar crystals located on a central measuring area corresponding to a gravity center position of the film forming region, whereby moisture resistance in the periphery of the panel is improved, so that a sufficient fluorescence lifetime of the panel as a whole is maintained.