Considering that the social influence due to a pandemic influenza that human being might be confronted with in the 21st century or an infectious disease spread by terrorism would be immense, it is recommended that we should know the results of the spread of disease in advance. Assuming that certain amount of persons are infected by an disease in an artificial society and that a model of disease spread using networks and its numerical simulation method are introduced, we may estimate the final stage of the pandemic. Using the results of such an analysis, we could prepare to the hazardous conditions in case of the outbreak by newly observed diseases or disease spread by acts of terrorism.