The present study investigates the impacts of increases in Research and Development (R&D, hereafter) on stock returns. The data is drawn from the database of Taiwan Economic Journal during the periods of 1998 to 2009. Following Eberhart et al.(2004), we employ calendar-time approach and the three-factor model (Fama and French, 1993) and the four-factor model (Carhart, 1997) to examine whether the abnormal returns exist after increase in R&D investment. Through the six-group portfolios according to firm characteristics, the present study provides the evidence that there are negative abnormal returns of stocks as the R&D expenditures increase, which is not consistent with Chan et al.(1990). Therefore, it might be negative impacts of R&D investment on stock prices of listed companies in Taiwan.