(57) There is disclosed an electron gun structure for color picture tubes comprising a prearranged electrode, a postarranged electrode, an extension flange perpendicularly formed along the periphery of the back end of said prearranged electrode, another extension flange perpendicularly formed along the periphery of the front end of said postarranged electrode, said both extension flanges being opposed to each other, and the electron beam passing apertures being disposed relatively inside said electrodes, wherein said prearranged electrode is supplied with a static voltage and said postarranged electrode with a dynamic focusing voltage which is varied according to a deflecting signal and a synchronizing signal, so that said prearranged electrode forms a convex focusing type of lens to have a focusing type of force which acts stronger vertically than horizontally, and said postarranged electrode forms a concave diverging lens to have a diverging force which acts stronger vertically than horizontally so as to expand the landing area of said electron beam vertically, thus said two lenses serving the complementary action to make the landing area of said electron beam circular throughout the screen of said color picture tube.