Remote sensing technology is useful for comprehending extensive damage caused by a tsunami disaster. In recent years, methods for detecting building damage due to tsunami disaster have been developed and the accuracies have been improved. X-band synthetic aperture radar (SAR) provides high-resolution spatial resolution which is sufficient for identifying building damage at a building unit scale. However, X-band SAR data has a disadvantage in the acquisition coverage which is smaller than that of L-band SAR data. On the other hand, to comprehend the damage of extensive tsunami affected areas, L-band SAR data which has lower spatial resolution is more effective than using X-band SAR data. To lead to an efficient emergency response or reconctuction activities after the disaster, these advantages and disadvantages are necessary to be clarifiled from the point of view of disaster management, and the appropriate method for applying the developed technologies in an efficient manner should be discussed. The primary objective of this study is to propose a rapid method to comprehend building damage by using L-band and X-band SAR data.