Electrical discharging machining (EDM) of carbon nano fiber (CNF) is introduced. CNF has been investigated as an emitter for field emission display (FED). For the uniform field emission, uneven CNFs need to be machined to uniform height. For the planarization of CNFs, EDM was used. EDM was conducted in air, unlike conventional EDM, to prevent the contamination of CNFs. For the uniformity of the machined surface, machining characteristics were investigated with applying different capacitance and voltage. With this method, the uniformity of field emission of CNFs was improved. Micro machining of CNFs was also studied.