MW selective heating is suggested to be occurred in microscale; however, it's impossible to measure a thermal gradient quantitatively in microscale by a conventional method. In addition, by conventional thermography, we cannot measure the materials temperature with different emissivity at the same time. Thus, selective-heating effect at the microscale is not understood well enough. In this study, the authors verify the elective heating effect using a high-resolution two-color thermography system. This system can measure the temperature on each pixel with ±2% accuracy with 8.8 µm/pixel. The results of the temperature distribution of at local areas clearly demonstrated that carbon powders were selectively heated. This selective heating resulted in local reduction at the contact point between C and a-Fe2O3, and carbon loss was enhanced because Boudouard reaction was more proceeded than other reaction.