Principle of the treatment of obesity is diet and exercise therapy. However, it is extremely difficult to maintain the effect in the long term. In recent years, mechanism of appetite center and adaptive thermogenesis is gradually clarified. As a tool of new treatment of obesity, anti-obesity drugs come to attract attention in this way. However, anti-obesity drug is not the all-around procedure that has got thinner easily if we use it. Anti-obesity drug should be used carefully to show the availability after having understood each action mechanism. Other than mazindol approved alone in Japan, we explain it in this chapter about sibutramine and rimonabant those are on the clinical trial now. We will mention an adaptation of a certain anti-obesity drug in the middle of an argument.