The development of techniques to determine the damage is required in order to prevent the destruction of structures for the save of human lives and the reduction of economic loss. In this study, we suggested a theoretical method to identify the damage location and the degree of damage using external and strain energy as a static characteristic, to be easier understood than the complex dynamic one. The proposed detection process of the damage location used the relationship between a damage indicator defined by the external energy and the loading location. The degree of damage was estimated by the energy principle. The strain energy was evaluated in the damaged and undamaged region respectively, in which the damage was considered as a reduction of the flexural stiffness. The selected examples of two- and three-span beams demonstrated the effectiveness of the proposed damage detection method.