An additive containing an ion as a luminescence center is added to alkali halide powder as a base material. Mechanical energy for applying an impact force, a shearing force, a shear stress, or a friction force is applied so as to grind or mix the alkali halide powder and the additive. The ion as the luminescence center is doped into the alkali halide as the base material so as to obtain alkali halide-based scintillator powder. With this process, the alkali halide-based scintillator powder can be manufactured at a room temperature in the atmospheric air without any complicated condition control or any process at a high temperature under high vacuum and a large-sized scintillator sheet can be produced.