We investigate the influence of heterogeneous beliefs on asset volatility when agents' degrees of confidence differ. With a continuous-time model subsuming agent's heterogeneous beliefs in the expected increase in dividends, a stock price formula is derived. Based on this formula, the stock volatility is computed via Monte Carlo simulation. The results show that the influence of belief heterogeneity in expectation on volatility depends on the confident agents' level of optimism. Empirical results are also provided.