Investment opportunity is the heart of the company's growth is that become important expectation which desired by the internal and external parties of company such as management, investors and creditors. The purpose of this study was to analyze the significance of the effect of IOS on the capital structure of the company. Object of this study is automotive and component companies and the research span was 2008-2012. The dependent variable of this study is the firm's capital structure, while the independent variable is IOS which consists of 5 single's proxy. The data used are secondary data from ICMD 2008-2012. The analytical tool used is a simple regression and factor analysis. The results showed that IOS significantly positive effect on capital structure. There are three viable IOS proxy used to form the joint proxy variables IOS that is E / P , MV / BVA and MV / BE. This study confirms that the proxy IOS with combined proxy better than a single proxy . This study also supports the pecking order theory than trade off theory regarding the relationship between IOS corporate capital structure.