Atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) were used to study optical fiber structures. The refractive index profile of fiber was disclosed by surface topography of etched fiber endface using a AFM. The difference of refractive index was resolved to 1 × 10 -6. Near-field optical intensity distribution at fiber endface has been successfully measured by a tapping-mode force regulated SNOM. Combination of tapping-mode AFM and SNOM allowed us to image both refractive index and near-field intensity structures of fibers simultaneously. The correlation between waveguide structures and near-field propagating modes was directly provided by this novel method. Results of single mode fibers and fibers with anisotropic structures illustrated the usefulness of this technique.