This study was based on the hypothesis that a fund manager has incentive to take more risk with funds to conceal his actual management ability. A theoretical model was built to test this hypothesis. According to the model, when a fund manager's ability is not observable, a poor fund manager may increase a fund's risk to conceal his real ability, so that poor performance may be attributed to external market factors rather than ability. Previous studies have usually suggested that the different risk-taking behavior of fund managers is encouraged by the asymmetric delivery of information on fund returns. Unlike previous studies, this study focuses on real-world situations where a fund investor has more access to information about fund returns, and his decisions are often affected by concerns about fund reputation. This study highlights the fact that a fund manager has incentive to utilize fund investors' imperfect preception on his own managerial ability even under the condition that fund returns are all disclosed to fund investors. Additionally, this study applies Korean Equity fund data to empirically demonstrate that funds with lower risk-adjusted returns take more risks in the next period than do those with higher risk-adjusted returns, a finding that supports the results of the theoretical model.