Concrete lining of underground structures is one of structural elements to require the structural integrity assessment. In this paper, for the structural-integrity assessment of concrete lining, the resonance search (RS) technique based on stress-wave propagation is proposed. The RS technique is the combination of the Spectral-Analysis-of-Surface-Waves (SASW) method and the resonance method. In the RS method, the shear-wave velocity profile is first determined by the SASW measurements. Then, the thickness of concrete lining is determined using the search technique to match the measured resonant frequency and the theoretical resonant frequency evaluated by the numerical modeling. The validity of the proposed procedure was verified by the numerical simulations of the method, the field test at a test concrete lining and the practical application to a real concrete lining of tunnel ManDeok in Korea. The slab thicknesses obtained by coring and Ground Penetrating Radar (GPR) scanning were also compared with the thickness by the RS technique.