The case study company is a semi-conductor manufacturer that produces semi-conductor devices according to customers’ demand. These devices are locally and globally supplied to various industries such as automotive and electrical appliances industries. Master production planning is necessary for the company to realize customer demands in a cost effective manner. By analyzing its historical data, it was revealed that the production amounts in some months were much lower than the capacity of the factory while the master plan of those months established prior to the actual production started at the beginning of the months indicated that the full capacity had already been committed, and vice versa. This inaccurate planning makes the company to substantially loose sales opportunity and profit. In this study, the current planning process of the company was thoroughly analyzed to pinpoint where the main deficiencies were. It was found that planning staff make their own plans and tolerances without considering holistic requirements. As a result, the restructure of the staff involved in planning decisions was necessary. New procedures and work instructions were developed according to the concepts of master production planning and rough-cut capacity planning for achieving centralize planning. Computer software was also employed to facilitate the planning process. The result indicated that the planning process is improved significantly in terms of shortened planning time and much more accuracy. Moreover, the company gained more effective capability to commit to customer’s demand.