Abstract: An apparatus for generating negative ions includes two casings which are coupled each other and respectively have an outer thread on one end thereof, a lid which is fastened to the coupled casings, an electrode rod disposed within the coupled casings, an electrode plate disposed within the coupled casings, a circuit board which is disposed within the combined casings and connected to the electrode rod and the electrode plate and having at least one high voltage discharging plate, a high voltage generator which is connected to the circuit board and the high voltage discharging plate, and a plurality of ventilation slots which are respectively defined in the casings and the lid, such that the apparatus can be easily assembled, installed and utilized as an independent unit.