To provide a method for producing a light-accumulating material which is excellent in an afterglow property, and which has high luminance.

In the production method for obtaining fine particles of the light-accumulating material, a material to be a mother crystal of the light-accumulating material, powder of an activating agent, powder of an auxiliary activating agent, and a reducing agent of the activating agent are put into a plasma atmosphere, and are melted and vaporized at a high temperature not lower than the boiling point of the raw material constituting the light-accumulating material so as to dissolve metal ions constituting the activating agent and the auxiliary activating agent in the form of a solid solution inside the mother crystal, and followed by quenching, Eu2O3 is used as the powder of the activating agent, a metal with reducing power stronger than that of EuO, e.g. Al, is used as the reducing agent, and a mixture with the metal, a mixture with the oxide of the metal, or an oxide of a material different from the metal is used as a material to be the mother crystal.