Provided are a rare earth activated alkaline earth metal fluorohalide stimulable phosphor exhibiting high image quality of radiation images and reduction of luminance degradation, and a radiation image conversion panel employing the stimulable phosphor represented by Formula (1) Ba.sub.(1-x)M.sup.2.sub.(x)FBr.sub.(y)I.sub.(1-y):aM.sup.1, bLn, cO, wherein M.sup.1 is at least an alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; M.sup.2 is at least an alkaline earth metal selected from the group consisting of Be, Mg, Sr and Ca; Ln is at least a rare earth element selected from the group consisting of Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er and Yb; and x, y, a, b and c are values meeting the following conditions: 0.ltoreq.x.ltoreq.0.3, 0.ltoreq.y.ltoreq.0.9, 0.ltoreq.a.ltoreq.0.05 0