In Taiwan, the main goal of the vocational education is to cultivate different kinds of professionals. Most of the teachings in the vocational universities or colleges focus on the trainings of different kinds of professional abilities, not on the character education. Therefore, few people are unable to resist the temptations or make the right decisions. They even break the laws and cause a great loss of person or enterprise and also cause a mess of our society. Professional ethics has become an important subject all over the world and also one of the main courses in the universities. In the universities, they offer courses on not only general ethics but also professional ethics in order to raise students' moral sensitivity. The paper is to discuss the teaching of professional ethics from the viewpoint of psychology in order to make the result of teaching more efficient.