Number of young investors in Indonesia stock market have significant increment in past three years, however, the financial literacy is still low. Recent studies showed that investors do not act rationally, their acts are subject to behavior bias meaning financial decision can be less than fully rational. Objective of this research is to analyze the impact of investment behavior biases from individual investors of stock market in Indonesia with demographic age below 40 years old. This study focuses on the impact of three independent variables namely heuristic, prospect and herding bias variables on one dependent variable stock investment decision while considering financial literacy as moderating variable. To test the proposed hypothesis, the primary data collection method was used. A sample of 118 individual stock investors was collected by purposive sampling through partial least square-structural equation modelling (PLS-SEM) analysis method. There is a significant relationship between the heuristic, prospect and herding variables on stock investment decision, which does not conform with previous studies. The study's findings are to give a contribution to investors in helping them make rational, reliable, and profitable judgments, policy makers, company, and other stakeholders on stock exchange.