An electron emission device includes cathode electrodes and gate electrodes formed on a first substrate and crossing each other while interposing an insulation layer. Opening portions are formed at the gate electrodes and the insulation layer while exposing the cathode electrodes. Electron emission sources are formed on the cathode electrodes exposed through the opening portions each with an area smaller than the area of the opening portion. An anode electrode is formed on a second substrate. Phosphor layers are formed on the anode electrode with a length extending in a first direction and a width extending in a second direction. Each electron emission source satisfies the following condition: a