In this paper, we have made some thin-walled box beams with varying cross-sections. There are three experimental examples. One is single-cell box beam, another is box beam with neck and the other is tapered box beam. We have tested to check the local deformation of these box beams visually near the resonant frequency band. We used a shaker to make harmonic movement to the supported end of beams and a digital stroboscope to check visually the local deformation of box beams. It is observed that mode shapes in experiment match well with those of simulation. This experiment is helpful to have a physical insight for the behavior of local deformations.