This thesis takes the penal data from 17 companies in Taiwan’s Biotechnology and Medicine industry as sample to estimate their investment behavior. The estimated results have shown that Tobin’s q does not significantly affect the investment ratio, while cash flow ratio and new debt ratio brings about significant effects with wrong signs during the period between 2003 and 2015. However, the sign of Tobin’s q has turned into significantly positive during the recent five years. Finally, is so far as the contribution to investment ratio is concerned, cash flow has played the most important role recently.