A new nondestructive inspection technique using infrared thermography was proposed, in which the thermal image of a heated test sample was used to identify flaws and defects. Joule effect heating by electric current was employed to heat up the sample instantaneously. Both numerical and experimental studies were made on the resolution and the applicability in the detection of the through-thickness and surface cracks embedded in steel plate samples. The results showed that a singular concentration in the surface temperature field was observed at the crack tips of the sample, and the cracks were found to be sensitively detected from the singular temperature field in the early stage of the heat conduction process. This technique was also applied to the inspection of the delamination defect in CFRP samples. The subsurface defect was found to be identified from a localized low-temperature region appearing on the sample surface. It was found that the proposed technique is applicable to damage inspection in CFRP as well as flow inspection in metallic materials.