An electron emission device includes a number of electron emission units, wherein each of the number of electron emission units includes a first electrode, an insulating layer, and a second electrode stacked in that sequence, wherein the first electrode is a carbon nanotube composite structure having a carbon nanotube layer and a semiconductor layer stacked together, and the semiconductor layer is sandwiched between the carbon nanotube layer and the insulating layer, the first electrodes in the number of electron emission units are spaced apart from each other, and the second electrodes in the number of electron emission units are spaced apart from each other.