隨著經濟發展、消費者的意識抬頭，顧客對於「品質」的要求日趨嚴苛，在自由競爭的環境之下，全球也逐步邁入微利時代，為了在競爭的環境下生存，企業如何降低成本、增加獲利與提昇競爭力便成為當前最重要的課題，近年來許多企業積極透過改善以突破逆境，而六標準差方法提供完整且持續的改善流程，成為許多企業奉行的改善工具。本研究主要為應用六標準差改善方法，透過個案研究的方式，實際改善個案鑄件公司之加工不良率，目的在於提昇個案公司產品良率、提升生產效率，減少顧客抱怨，進而提升其在產業中的競爭力。

With the development of economy and the rise of consumers' awareness, customers' requirement toward ＂quality＂ becomes increasingly stringent. Under the environment of free competition, the world also steps into the slight-profit era gradually. In order to survive in this competitive environment, how the companies decrease cost, increase profit and enhance competitiveness become the most important issue. Recently, many companies make improvement actively so as to break through the adversity, and six sigma approach provides complete and continuous improvement process, becoming the improvement tool pursued by many companies. This study mainly applies six sigma approach to improve the processing defect rate of a casting company via case study, with the purpose to improve the product yield rate, enhance production efficiency and decrease customer complaints so as to enhance its competitiveness within the same industry.