An electron gun for a cathode ray tube includes a cathode for radiating electron beams, a scanning velocity modulation coil for synchronizing the electron beams with an image signal, a focus electrode having first and second sub-electrodes disposed with a gap through which a magnetic field generated by the scanning velocity modulation coil passes, a plurality of grid electrodes with the focus electrode for controlling the electron beams radiated from the cathode, a support for aligning and supporting the grid electrodes, and a shield electrode electrically connected to the first and second sub-electrodes to protect against infiltration of an outer electric field. The shield electrode includes plural intermediate electrodes disposed in the gap between the first and second sub-electrodes, and electrical connecting unit for electrically connecting the intermediate electrodes to the first and second sub-electrodes. The intermediate electrodes are spaced away from each other.