A gradient-index optical element comprises SiO2, BaO, and TiO2 as essential components, and has a refractive index profile in its diametrical direction. The molar ratio of barium to silicon at the center of the element in its diametrical direction is limited to Ba/Si≧0.4. This gradient-index optical element has a small refractive index difference with reduced chromatic aberrations and, hence, is suitable for use with optical equipment.