<p>A plastic optical fiber low in transmission loss in a high-order mode and small in mode dispersion. The plastic optical fiber comprises at least a core and a clad surrounding the core, characterized in that the core has a refractive index gradually decreasing from the core center toward the outside in the radial direction of the fiber, and the refractive index of the clad is lower than that of the core center and higher than that of the core periphery.</p>
