A nitride semiconductor ultraviolet light emitting device 1 is configured such that a nitride semiconductor ultraviolet light emitting element 10 is mounted on a base 30 by flip-chip mounting and sealed with an amorphous fluororesin whose terminal functional group is perfluoroalkyl group. The nitride semiconductor ultraviolet light emitting element 10 includes a sapphire substrate 11, a semiconductor laminated portion 12 of an AlGaN-based semiconductor laminated on a front surface of the sapphire substrate 11, an n electrode 13, a p electrode 14 and a back surface covering layer 15 which is formed on a back surface of the sapphire substrate 11 and transmits ultraviolet light. The back surface covering layer 15 has apertures 16 through which a part of the back surface of the sapphire substrate 11 is exposed, the apertures 16 is uniformly dispersed or distributed on the back surface of the sapphire substrate, a cross-sectional shape of the apertures 16 vertical to the back surface of the sapphire substrate 11 has a portion where an aperture width of a part close to the back surface is wider than an aperture width of a part far from the back surface, and the amorphous fluororesin covers the front surface of the back surface covering layer 15 and fills insides of the apertures 16.