Investing in stock has become a common thing for investors. The aim of investors in investing in stocks is to get a return, either in if capital gains or dividends. To get profitable investment, investors must be able to analyze their investments. Return the value of the firm is reflected by the value of the firm which valuable in the market. Firm value as measured by Tobin's Q is affected by several factors such as investment opportunity set, debt ratio and dividend policy of the firm. This study aims to measure the effect of the investment opportunity set (IOS) and debt ratio to the value of firm with dividend policy as intervening variable. IOS is measured by market to book value of assets ratio, market to book value of equity ratio, and EPS/PRICE. Debt ratio is measured by debt to equity ratio, while dividend policy is measured by using the dividend yield. This study used secondary data which taken on an annual basis from 2011 to 2013. The data used as the sample firms are all industries that listed in the Indonesian Stock Exchange except for the banking and other financial institution industry. Test for the model coefficient were conducted by regression and path analysis. The findings of this study showed that IOS has significant effect on firm value. While the dividend policy has a positive significant, on debt ratio and firm value, while the debt ratio has a positive significant effect on firm value. The conclusions of this study explained that the positive effect on firm value is not IOS increasingly significant when the company decides to pay dividends.