Recently, risk management for the disasters such as earth quick, mountain explosion, seismic sea wave, in addition to ordinal disasters, such as typhoon, rain flooding and snow-slide has been seriously concerned to keep the safety for the residents in many countries. More reliable and robust information system than the conventional business or research oriented information networks must be constructed to normally and correctly perform their functions for residents even though serious disaster happened. In this paper, we propose a unified Wide area Disaster information Network (WDN) using Internet based on the combination of both wired and wireless networks. The system requirements and their functions of WDN are precisely defined and the various types of information for residents are precisely defined. The prototype system of the disaster information system based on our suggested WDN was built to demonstrate and evaluate its functionality. Through the practical training in the local city for preparation of mountain explosion, we could confirm the usefulness of our suggested system.