This study proposes a safety route guidance system used after a natural disaster by gathering sensing data from pedestrians' smartphones. In order to find the problems caused by a disaster such as collapsed house, fissures and floods, the system uses the information retrieved from pedestrians' smartphones with GPS receivers and accelerometers. In addition, the system does not use the information from the map data before the disaster for detecting the geographical information in case of large-scale disasters. Therefore, the map data after a disaster is mapped with only the information after the disaster. As a result, pedestrians' moving paths and walking states are evaluated and used for evacuation guidance.