Cherenkov phase-matching terahertz-wave generation is attractive way of efficient THz-wave generation. Efficient THz-wave generation by nonlinear optics has two problems, strong absorption and strong dispersion of many crystals. These problems can be overcome by Cherenkov phase matching. We successfully demonstrated wide tunable monochromatic THz-wave generation about from 0.2 to 7.2 THz using waveguided lithium niobate crystal. The Cherenkov process is useful for novel THz-wave detection method. THz-wave and optical waves in nonlinear optical process are strongly correlated. Thus, THz-wave information can transfer to pump and signal wave. THz-wave generated by Cherenkov phase matching can be used as evanescent-probe at interface facet of the crystal. Phase shift and attenuation of reflected THz-wave has information of a sample set at the interface, so the information can be detected by optical analysis for pump and signal wave.