It is considered that a minimum level of safety is ensured for ships by complying with the regulations. International regulations for ships are developed by the International Maritime Organization (IMO). Formal Safety Assessment (FSA) is a rule-making tool in the IMO to develop reasonable international regulations considering the impact of the regulation from the viewpoint of safety and economy. In order to consider the aspects of safety and economy during the rule-making, risk assessment and cost-benefit assessment are conducted in the FSA. In this paper, the outline of FSA is introduced as an example of efforts to ensure the safety of ships from the viewpoint of international regulations.