In this study, first, the optimum adoption of singular values was investigated by a numerical example when the unknown parameters were the nodal forces of a finite element. It was shown that the distribution of the singular values depended on the sensor location and that accurate estimation results could be obtained by using one singular value in this example based on the condition number. Then the new expression of the virtual additional force was proposed. That is one of the regularization methods of inverse analysis, and the magnitude of the impulsive force is set as an unknown parameter. The numerical example showed that the estimated location of the abnormality determined by the proposed method agreed with that determined by the adoption of one singular value using the previous method in which the nodal forces were set as the unknown parameters. Also, the numerical and the experimental results showed that the accurate estimated location of the abnormality could be obtained by adopting one singular value using the proposed method. As a result, it was shown that the proposed method could be used in the actual application.