Recently, the Infrared Thermography Technique is widely used for nondestructive testing (NDT) of structures due to its convenience. In particular, various techniques have been applied to detect imperfections such as concrete surface defects and welding defects of steel structures. The crack of concrete structure and connection defects of steel structure plays an important role in the durability and safety of structure. Therefore, structures should be measured periodically to assess potential problems in durability. Conventional measurement systems depend on visual inspection and NDT system such as radiation inspection, ultra sound inspection, magnetic particle inspection and penetration inspection. However, conventional measurement systems require prolonged inspection time because the area measurement is narrow, which leads to an increase in cost. In addition, Conventional measurement systems have difficulties in measuring tall structures. In order to solve these problems, Infrared Thermography Technique has been developed as NDT method, but it has not reached the practical application yet. Therefore, this paper is part of a study to detect defects in weld zone in steel structures and to detect crack defects in concrete structures using Infrared Thermography Technique. The temperature on steel and concrete structures surface depends on the material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Test specimens were prepared with artificial defects, then passive and active methods were used to determine damages on the structures, as well to detect defects. As a result, defects were observed by comparing infrared thermal images and surface temperature data of the defected area in comparison to the normal area. Furthermore, defects were measured using the standard deviation of the temperature corresponding to the defected area. It is confirmed that the defect can be judged when the standard deviation of the temperature corresponding to the weld is 3 or higher. In addition, various preliminary experiments have mentioned guidelines of damage evaluation of the structure using Infrared Thermography technique. Finally, based on the results of this study, it is confirmed of the possibility of evaluating the damage of the structures using the Infrared-Thermography Technique. In order to obtain quantitative results of the defected area, additional studies should be conducted adding different variables.