This paper describes a new health monitoring method using operational transfer path analysis for operating machine and infrastructure. At first, vibrational characteristics of the operational transfer path analysis to a two-beam structure consists of difference sections are shown. And then, the health monitoring method identifies damage location and damage extent using the operational transfer path analysis is proposed. The newest method is validated through numerical analyses, using a finite element method of a simple structure consisting of one-beam structure including the young's modulus of one part of element changed. As a result, the effectiveness of the method is verified.