To provide a photostimulable phosphor which is excellent in photostimulation luminescence intensity, shows little X-ray damage, and has a good granularity; a manufacturing method for the phosphor; and a radiological image conversion panel.

In the manufacturing method for the photostimulable phosphor of the formula (1): (Ba1-xM1)FBryI1-yX:aM2, bLn, cO (wherein M1 is at least one alkaline earth metal atom selected from the group consisting of Mg, Ca, Sr, Zn, and Cd; M2 is at least one alkali metal atom selected from Li, Na, K, Rb, and Cs; X is at least one halogen atom selected from Cl, Br, and I; Ln is at least one rare-earth atom selected from Ce, Pr, Sm. Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb; and (x), (y), (a), (b), and (c) satisfy the relations: 0≤x≤0.3, 0≤y≤0.3, 0≤a≤0.05, 0<b≤0.2 and 0<c≤0.1, respectively) performed in a liquid phase, a step wherein an aqueous solution of an inorganic fluoride is added to an aqueous barium halide solution to obtain a precipitate of a precursor crystal of the photostimulable phosphor and a step wherein a solvent is removed from the reaction liquid are simultaneously performed to obtain the precursor of the photostimulable phosphor.