This paper identifies that investors' net-buy factors can be used to common factors that can explain common fluctuation of stock returns in Korean stock market. This paper uses the cross-section regression approach of Fama and MacBeth(1973) in Fama and French(1992) and the time-series regression approach of Black, Jensen, and Sholes(1972) in Fama and French(1993). The main results of the paper are as follows. First, the results on Fama-MacBeth regressions say that B/M and FNB are explained the cross-section of average stock returns. Second, for results on time-series regressions, it shows that regression coefficients of investors' net-buy factors(FLMH, TLMH, DLMH) have certain patterns. But in view of statistical significance, it's not good enough. Third, Investors' net-buy factor models are quite significant. But it isn't improved so far compared to Fama-French 3 factor model.