A sunk cost fallacy is a fallacy that people choose irrationally considering the sunk cost, even though they must make irrational decisions by comparing marginal benefits and marginal costs that will occur in the future. Not only individuals, but investment decisions by firms and government’s policy decisions often suffer sunk cost bias, causing economics to regard sunk cost as a key concept. This study, by examining previous studies on sunk costs, aims to achieve three objectives. The first one is to identify and categorize the causes of sunk cost fallacy. Non-maximizing human, loss aversion, entrapment, and reputations are among them. Secondly, this study also grasps how age, intelligence, intellectual level, cultural background, and projects are related to the sunk cost fallacy. Finally, some implications for economic education are drawn. One way that is known to be effective in relieving suck cost bias is to emphasize the costs of continuing explicitly. Setting explicit budgets also helps to sunk cost effect by de-escalating. Making people aware of various costs of the choices, internalizing the principle of no free lunch, and developing habit and attitude to explicitly set budgets before making decisions and to track costs are required.