A dielectric device of higher performance is provided. An electron emitter, to which the dielectric device is applied is provided with: an emitter including a dielectric; and an upper electrode and a lower electrode to which drive voltage is applied in order to emit electrons. The emitter is formed by the aerosol deposition method or the sol impregnation method, and the surface roughness of the upper surface thereof is controlled in the range from 0.1 to 3 in Ra.