Investors purchase equity shares of enterprises, injecting their money and wealth in the hope of efficient outcome and profits. Meanwhile, the companies can transfer the money into other companies, even a remote country, without the consent of small investors, solely on the approval of board of directors. The money transferred into other companies lacks proper monitoring and management, resulting in many financial fraud and scandals. This study focuses on the purposes of enterprise equity investment behavior as well as relevant law regulations. Collecting the money outflow caused by equity investment from cash flow statements of Taiwan public listing companies, this study investigates the response of stock price return as well as stock prices by employing panel data regression model. The result shows equity investment activities have negative effects on stock prices. Considering lack of proper monitor, investors downgrade the valuation of companies that transferred money into other entities.