To obtain a blue fluorescent substance for a low voltage, excellent in improving effect on luminance by including an adequate amount of phosphorus P on the surface of the fluorescent substance.

This blue fluorescent substance for a low voltage contains P in a proportion of 0.5-3 wt.% in the fluorescent substance comprising a zinc oxide and a gallium oxide. Preferably, the zinc oxide is ZnO, and the gallium oxide is Ga2O3. The molar ratio of the zinc oxide to the gallium oxide is preferably 1:1.