PROBLEM TO BE SOLVED: To enhance the reliability of an investigated result by an infrared investigation method. SOLUTION: Testing objects 10, 10' are installed on different ground surfaces under the environmental conditions same respectively to investigation objective portions 21, 22. The investigation objective portion 21 under the environmental condition same to the testing object 10 is photographed by an infrared camera, in the timing when a temperature difference between a sound part and a damaged part obtained from a detection result of a temperature sensor in the testing object 10 comes to a prescribed value or more. A surface temperature distribution of the photographed investigation objective portion 21 is analyzed, and a damaged state of the actual investigation objective portion 21 is judged based on a corresponding damage pattern. COPYRIGHT: (C)2005,JPO&NCIPI
