Our research group previously developed a system that checks Twitter tweet contents for current-location address using GPS and for need of assistance, and automatically attaches a hashtag to postings made within the system. In the present study, we proceeded to the construction of a disaster mitigation support system that utilizes tweets posted in the system together with web services in order to transmit information for disaster mitigation. The new system draws concurrently from some of the many web services related to disaster mitigation and is characterized by its transmission of information on specific locations obtained by GPS. Incorporating a web GIS, the system uses a web API to convert location geocoordinates (latitude and longitude) to prefectural names and vice versa, as well as to construct a map showing radar-detected rain cloud information. Furthermore, it uses Python to obtain tweets and weather information, convert location indicators, and create HTML files.