Engineering ethics is an inter-disciplinary subject developed in the late 20th century. But many engineers doubt how engineering connects with ethics. This paper analyses the view of engineering as application of science and the view of engineering as mere instrument for human values. Engineering is not an application of science to make risk-free products but risk-involving inherently and has great ethical implications. Engineering is more than an instrument for human values. On the contrary it has great reaction on social values. Engineering ethics should be studied on the basis of the interrelation of engineering and society. Within this framework engineers' responsibility is discussed.