Evacuation is one of the most important aspects among the disaster response activities by local municipalities in time of severe weather. Japanese national laws put responsibility of evacuation order on local mayors. Decision making by local mayors and their subordinates has been supported both by warning provided by various sectors of national government and by hazard and risk information uncovered by researchers. A series of field interviews to 24 local municipalities across the nation was conducted to clarify the decision structure in terms of perceptive costs and losses. Number of personnel actively put into operation in pre-disaster stages and expected losses in local officials' cognition were numerated. Major obstacles to issue an evacuation order were listed out. These factors, analyzed by a decision tree, reveal what hinders evacuation judgment. Uncertainties entailing to expected casualties and inaccuracy of warnings keep local officials from the issuance of evacuation order through higher costs of explanation. The costs of explanation can be reduced by combined efforts to clarify expected losses and to raise accuracy of warnings. Importance of further research on risk communication based on quantitative hazard identification and risk analyses was brought to our attention.