an electron gun for a cathode ray tube is disclosed , which has a simple structure and can prevent the spot on a screen from being degraded . in the electron gun for a cathode ray tube including a cathode that emits electron beams , a first electrode that controls the electron beams emitted from the cathode , a second electrode that accelerates the electron beams emitted from the first electrode , and third to fifth electrodes sequentially arranged in a screen direction to act as pre - focus lenses , the electron gun is characterized in that the third to fifth electrodes have different sized electron beam through holes .