In recent years, numerous damages in the RC slabs of road bridges due to increasing traffic volume, over-weight vehicles and salt damage caused by anti-freezing agent have been reported. Therefore, development of an effective non-destructive inspection method for detecting such damages in concrete slabs beneath asphalt pavement is essential. Among various methods, the infrared thermography method enables non-contact and traveling investigations to be conducted for wide area of road bridges in a short time. Using this advantage, we developed a detection system for damages in RC slabs beneath asphalt pavement utilizing infrared thermography. The developed system can prevent degradation of thermography data based on extended exposure time by overlapped capturing of ten images from high-speed moving vehicles and can automatically generate a highly comprehensive panoramic image. Visible images of the road surface can also be acquired at the same time, making it possible to more accurately determine obstacles in the RC slabs beneath asphalt pavement.