Thermal camera have been used to monitor thermal anomaly. But It is difficult to monitor a wide range because camera angle is narrow. In this study, we propose a robotic thermal observation system in consideration of 3D mapping for the geometry of the real environment. It is possible to combine thermal and RGBD camera information by having a calibration process with a thermal pattern. By integrating the camera system with a mobile robot, we are able to obtain a wide-area thermal map with 3D geometry. And the system performs visualization of the temperature change by comparing the 3D thermal model and current temperature.