This report explores the relationship between fund flow and performance in the mutual funds and private pension funds from 2010 to 2017. Empirical results show that the overall performance of corporate pension funds was lower than the mutual funds, since the proportion of domestic equity funds in private pension funds was low when the returns of domestic equity funds were high, but corporate pension funds showed higher performance than mutual funds in each asset category. This study finds that there existed the convex relationship between fund flow and performance in private pension funds and mutual funds. That is, investors sell low performance funds less, and buy high performance funds more. The convexity between fund flow and performance implies that private pension fund managers do not play their roles properly in reflecting investors’ interests, and the major investment decisions are made by individual investors who have insufficient information. Therefore, the roles of investment managers in private pension funds and the investment advisors should be enhanced to help investor make rational investment decision.