A method of detecting a defect on the surface of a structure using an infrared radiometric thermometer. It is determined that there is a lifting defect at a region of the surface if the region has a temperature difference of 0.3 DEG C. or more in comparison with a surrounding region and has an area of 200 cm2 or more. The temperature of the surface of the structure is obtained using the infrared radiometric thermometer in a period of time from 19:00 p.m. on a day when it is clear at least in the daytime to 4:30 a.m. on the next day.
