An apparatus of the field emission light source having a luminous area and a non-luminous area includes a first plate, a second plate, cathode structures, gate structures, emission sources, an anode layer, a fluorescent layer, a getter, a retaining device and a sealant. The cathode structures are disposed in the luminous area and on the first plate. The emission sources are disposed on the cathode structures. The anode layer is disposed on the second plate. The fluorescent layer is disposed on the anode layer. The getter is disposed in the non-luminous area and on one of the first and the second plates. The retaining device is disposed between the luminous area and the non-luminous area. The sealant is sandwiched between the first plate and the second plate. When activating the getter, the retaining device can prevent metal ions gushed from the getter from entering the luminous area.