An electron gun for a cathode ray tube having a scanning velocity modulation coil mounted on an outer circumference of a neck of the cathode ray tube. The electron gun includes a cathode for emitting electron beams; a plurality of grid electrodes sequentially mounted starting from the cathode, and including a plurality of focus electrodes mounted with a predetermined gap therebetween; supports on which the grid electrodes are fixed in a row; and a shield electrode mounted between the focus electrodes and connected to the focus electrodes. The shield electrode defines a continuous space along an elongated axis direction of the cathode ray tube.