An electron emission device exhibits a high electron emission efficiency. The device comprises an electron supply layer of metal or semiconductor, an insulator layer formed on the electron supply layer, and a thin-film metal electrode formed on the insulator layer. The electron emission device emits electrons when an electric field is applied between the electron supply layer and the thin-film metal electrode. The insulator layer is a dielectric layer having a thickness of 50 nanometers or more, and formed by a vacuum evaporation process with a layer forming rate of 0.5 to 100 nanometers/minute.