Overconfidence has been widely document in the both psychology and financial literature. However, previous empirical researches have mainly focused on the market data to analyze the investors’ behavior in Taiwan stock market. Only a few studies have been looked into the investors’ other psychological biases and demographic information(gender, age, income, education…). In addition, these characteristics may have some effects on the investors’ trading behavior. Therefore, this study explores overconfidence not only via market data but personal characteristics. A questionnaire was used to investigate what are manager’s tendencies of financial behavior. The results of this study have found that the overconfidence is widely observed on the Taiwanese investors and help investors to get a complete understanding of non-rational side of people.