The time change in data measured by infrared thermography is used to analyze thermoelastic stress. Displacement caused by the load on the measurement object is the cause of the apparent temperature change. To prevent this, it is effective to photograph the measurement object with a visible camera synchronized with the infrared thermography. The displacement of the measurement object calculated from the visible image is converted to the movement in the infrared thermography, and the displacement is corrected. In this study, a system was developed using thermoelastic stress analysis (TSA) to measure temperature changes due to the load when a car passes over a steel bridge.