This paper presents an experimental and analytical study on how to identify the deterioration points of bridges using the rate of change of deflection influence lines and deflection curves. In the experiment using aluminum H-beams, the stiffness was changed by attaching aluminum steel plates instead of deteriorating the structural members. Although there was little difference in the natural frequencies of the two structures due to the change in stiffness, it was confirmed that the change rate of the deflection influence line could be used to identify the location of the stiffness change. In addition, it was found that the rate of change of the deflection curve obtained from the experimental results and the elastic analysis results of the two-dimensional FE analysis could be used to identify the location of shear cracks in the loading test of RC beams with shear failure precedence.