本文旨在探討不同類型的投資人(外資、國內法人、自然人)在其前一期具有正報酬的條件下，在下一期再投資時，其行為是否有過度自信的現象發生。
本文是以台灣期貨市場為例，並以2007年1月至2009年12月為區間來研究，並且用交易不均衡(TIB)作為變數來衡量投資人過度自信的程度。
交易不均衡是用來判斷投資人是買方或是賣方，無論投資人前一期的報酬是由於看漲或是看空市場，只要前一期有獲得正報酬，其下一期再投資時，若下單的方向與市場價格變化不相符則我們稱投資人具有過度自信的現象。
我們發現這三種類型的投資人在前一期獲得正報酬之後，在下一期的投資行為皆出現過度自信的現象，除了外資在市場狀況不明確時沒有出現過度自信，其餘結果皆為顯著，表示投資人在自身獲利後更相信自己判斷市場趨勢的能力。

This study aims to examine whether different type of investors (foreign investors, domestic institution investors, retail investors) are overconfident when they have return from former period and then invest in the following period.
This paper takes the Taiwan futures market as an example and use the period from January 2007 to December 2012 and use Trade Imbalance (TIB) as the variable to measure the degree of overconfidence.
TIB is used to determine whether investors are buyer or seller. No matter their return from former period was due to long or short position, as long as they got return from former period and the market trend they predict is not the same with actual market then they are overconfident.
The regression results show that these three types of investors are all have the tend to be overconfident at a significant level except foreign investors’ result of a period when the market condition was not clear which means that investors are more confident about their ability to forecast market price after getting profit form former period.

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