A process for producing a Group II metal sulfide phosphor precursor, comprising adding to an organic solvent an aqueous solution containing at least one of a Group II element compound, a sulfurizing agent, and a compound containing any of copper, silver, manganese, gold, and rare-earth elements to obtain a reaction mixture, heating the reaction mixture to produce an azeotrope of the water and the organic solvent, and removing water from the reaction mixture to produce a desired Group II metal sulfide in the reaction mixture, wherein the removal of water from the reaction mixture occurs by recovering only the water condensed from a vapor produced by the azeotropic distillation.