The photoinduced modification of the near-surface region of K3C60 samples generates very large enhancement of the diamagnetic shielding fraction (chi(sf)) value. Before illumination, only similar to 10 vol % of the K3C60 quenched sample exhibited diamagnetism. However, after illumination, values close to 100 vol % of chi(sf) were obtained, however, Tc was not significantly changed. Furthermore, chi(sf) was found to return to its original value upon heating, demonstrating that the transformation is reversible. The Raman measurements indicate that this reversible behavior is due to photopolymerization and thermal depolymerization of C-60 molecules. These results indicate that the surface modification provides new ways to address important fundamental science and technological issues pertaining to this class of materials.