This research aims to examine the level of voluntary disclosure in annual reports prepared by Manufacturing listed firms on IDX on the year of 2014 and the influence of corporate governance mechanism (board size, audit committee, and ownership concentration) towards voluntary disclosure level. Sample was selected using proportionate stratified random sampling method and 30 companies are collected. Content analysis is used as a tool for data collection to examine the level of voluntary disclosure expressed on firm’s annual report. We find that the average level of voluntary disclosure disclosure is 37,53% which is classified as low. Applying multiple regression analysis and using Ftest and t-test with significant level at 5%, we also find that board size has positive and significant influence on voluntary disclosure level. The implication is that big and effective designed board are more concerned to increase voluntary disclosure, in order to reduce asimmetry of information between firms and users and increase credibility and accountability of the firms.