A field emission device includes a substrate (11) and a carbon nanotube array (12) formed thereon. Carbon nanotubes (120) of the carbon nanotube array are parallel to each other and cooperatively form a plurality of substantially rod-shaped lower portions (121, 121') and a plurality of corresponding tapered tips (122, 122') above the lower portions. Each lower portion and tapered tips have a plurality of carbon nanotubes. Distances between adjacent tips are approximately uniform, and are more than one micrometer. Preferably, the distance is in the range from 1 to 30 micrometers. The field emission device with this structure has reduced shielding between adjacent carbon nanotubes and has decreased threshold voltage required for field emission by the carbon nanotubes. The field emission device also contributes to an improved field emission concentration and efficiency.