The impact acoustics method using a hammer on the surface of airport flexible pavements is used to find layer debonding between asphalt concrete layers. However, it takes many days to investigate the existence of layer debonding in a huge area in an airport with the impact acoustics method. As surface temperature on the debonded area tends to decrease in the night time compared with that on the non-debonded area, field tests on the airport were conducted to verify the applicability of inspection with infrared thermography. As a result, the following conclusions were obtained: (1) It is confirmed that layer debonding at the depth of 40 mm – 70 mm from the surface of pavements can be found by surface temperature differences measured by infrared thermography; (2) Existence of rubber on the surface of the runway makes it difficult to identify the layer debonding by infrared thermography, though the effect of grooves on the surface of the runway is not large; (3) From the results of field tests and thermal analysis of the flexible pavement, the volume of solar radiation and the difference between maximum and minimum temperatures in a day affects the surface temperature difference between debonded and non-debonded areas.