In recent years, our lives become more convenient rapidly due to progress of technology. There are, however, various sources of uneasiness and anxiety still now. Previously researchers believed that no-trouble system provided a sense of safety and reliability to people. But recently they begin to realize that people don't feel relieved even if the accident probability of the system is very low. The purpose of this paper is to consider the structure of sense of security for people and propose an approach to diminish the anxiety of people's mind.