The aim of this study is to examine the effect of good corporate governance mechanism to stock performance through sustainability report disclosure as mediation. Good corporate governance mechanism used in this case is commissioner board's size, the proportion of independent commissioners, audit committee's size, and managerial ownership, whereas stock performance measured in this case is stock return. Using a sample 113 companies all sector listed in Indonesia Stock Exchange which publish sustainability report during 2014-2016. This study were using simple and multiple linear regression analysed to determine indirect effect through path diagram. Based on the result of the first hypothesis testing of GCG mechanism none of which have significant effect on SR disclosure, the second hypothesis is only the proportion of independent commissioner and audit committee's size of GCG mechanism which have positive significant effect on stock performance, the third hypothesis of SR disclosure has no significant effect on stock performance and the fourth hypothesis explains that SR disclosure is not exactly a mediating variable.