This study attempted to explain the venture bubble as a result of the over-reaction of venture market. I, according to the methodology of De Bondt and Thaler(1985, 1988), tested the price reversal of monthly abnormal returns of venture business stock prices from January, 1999 to December, 2004. The portfolios of the stocks that realized positive anormal returns showed statistically significant price reversal which can be the evidence of over-reaction. Contrarily, the portfolios of the stocks that realized negative anormal returns showed a sign of under-reaction. This result can be interpreted that investors of venture business have over reacted to positive informations, and under reacted to negative informations. Next, I investigated the difference of price reversal between bubble period(1999~2000) and non-bubble period(2001~2002). I found that the over-reaction is concentrated at the period of venture bubble. This result show that the over-reaction of venture investors is related to venture bubble.

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