In the case of large scale disaster, such as earthquake, volcanic explosion, sea wave, more robust and flexible nation-wide disaster information network is required not only for governmental supporters but also residents and volunteers than business oriented network to communicate each other even though some parts of the network and information system are destroyed and disconnected. In this paper, we introduce a larger scale distributed disaster information network system based on mobile ad hoc network (MANET) and overlay network. MANET is used for the access network for residents and volunteers around the disaster area and evacuation places. The evacuated residents and volunteers can flexibly communicate with others though MANET using IP based terminals, wireless IP telephones and mobile PCs. On the other hand, overlay network is applied for national wide government and local government network to provide robust and redundant large scale disaster information network. By combining with both MANET access network and overlay network, more robust and flexible, and large scale disaster information network system can be realized provide even some of network lines and nodes are damaged and destroyed when the disaster happened.