An electron gun for a color cathode ray tube is formed with a control electrode, an accelerating electrode, an anode, and a focusing electrode divided into a first and a second focusing electrode. A static focusing voltage predetermined independently of a deflection period is applied to the first focusing electrode and a parabolic waveform dynamic focusing voltage varying according to the deflection period is applied to the second focusing electrode. The first focusing electrode has three electron beam apertures with vertical parallel plates mounted around each aperture in a direction opposite to the direction of the electron beams. The second focusing electrode has three electron beam apertures with horizontal parallel plates mounted around each aperture in a direction opposite to the direction of the electron beams. The centers of the left and right electron beam apertures are offset to the left and right sides of the central axis of the vertical and horizontal parallel plates. This configuration allows easy assembly and produces a vertical elongated electron beam even with low dynamic voltage V.sub.d and thereby improves the focus of the electron beam.