Are stock market investors concerned with obtaining abnormal returns by acquiring certain information? This paper studied the effect of ex-dividend date for cash-dividend policy. We try to demonstrate the existence of abnormal returns by examining stock trading situations before and after the ex-dividend date. We find that abnormal returns exist for listed Taiwan firms before and after the ex-dividend date. If an investor buys the stock of a firm who adopts a cash-dividend payout at the closing price 11 days before the ex-dividend date, and sells them at the closing price 10 days after the ex-dividend date, the investor will obtain an average 2.13% abnormal return, regardless of the transaction cost. This paper further analyzes whether firms adopting cash-dividend payouts have different abnormal returns on stock price performance depending on different variables. Yilmaz and Gulay's (2006) method of analyzing abnormal returns of stock prices was adopted. Further studies were undertaken of the three dimensions of cash-dividend payout ratio, stock trading turnover rate, and the firm size.