The main goal of this dissertation was to realize a fully automated and robust dual-tip scanning near-field optical microscope (SNOM) and demonstrate its capabilities to characterize nanophotonic systems. The dual-tip SNOM accesses optical information not simply attained with other super-resolution microscopy techniques. This work thoroughly explained the implementation of a collision prevention scheme and the realization of the fully automated dual-tip SNOM, in which the detection tip automatically scans the entire area surrounding the excitation tip without collision. After successfully implementing the automated dual-tip SNOM, the setup was utilized to measure the near-field of different photonic materials. First, the dual-tip SNOM was used to explore the polarization characteristic of the emission from the bent fiber aperture tip through exciting surface plasmon polaritons (SPPs) on an air-gold interface. Another unique application of the dual-tip SNOM is to excite the edge or corner of a photonic system locally. The automated detection tip was used to map a complex near-field pattern due to the excited SPPs and reflected SPPs from the edges of the truncated triangular gold platelet. The most distinguished capability of the automated dual-tip SNOM shown in this thesis is spectral- and spatial-dependent near-field measurements of a nanodisk metasurface as a nanostructured sample. In spectral-dependent near-field measurements, the excitation tip illuminated the silicon metasurface at different wavelengths. In spatial-dependence near-field measurements, the fixed excitation wavelength was used to measure the position-dependent near-field intensities when the metasurface was displaced relative to the excitation tip. It was demonstrated that the integrated measured near-field intensities by the detection tip could be related to the metasurface's partial local density of optical states at the excitation tip's position.