This study explores the theory and practice of business ethics. By ethics is meant a behavioral code that conforms to the moral standards required for certain interpersonal relations, and by business ethics is meant such ethical values and principles as are expected of companies and enterprises in its practice of business. As the times evolve, civil society and the public are demanding higher business ethics; accordingly, maintaining sustainable business ethics has become an important strategy for corporate entities to gain competitive strength. The study first explains the concepts and principles of ethics and discusses what business ethics has to contain. Then, after analyzing why business ethics are on the decline in the industrial society, the work proceeds to deal with how to reconstruct the required ethical elements and values. A case study is finally made of Taiwan Semiconductor Manufacturing Company, Ltd. in terms of the practice of business ethics.