Abstract: A large-area and high-luminance deep ultraviolet light source device is provided under circumstances where the scales of existing mercury lamps used as ultraviolet light sources cannot be reduced and light-emitting diodes of 365 nm or less do not reach the practical level. The deep ultraviolet light source device comprises at least an anode substrate having an ultraviolet phosphor thin film doped with rare-earth metal ions such as gadolinium (Gd) ions and containing with aluminum nitride as the host material, a cathode substrate having a field electron emission material thin film, a spacer for holding the anode substrate and the cathode substrate opposite to each other and maintaining the space between the substrates in a vacuum atmosphere, and a voltage circuit for applying an electric field to the space between the anode substrate and the cathode substrate.