Darwin's attempt is to provide a foundation for explaining the moral characteristic of human beings from an evolutionary point of view, through methods like comparison to animals, observation of intuitive moral judgment, and cross-cultural comparison: these methods should be examined closely. First of all, we have to make sure that it is not innateness of morality that is exhibited through comparison with animals, nor can we say morality resulted from social instinct which we share with animals. Because the mechanism of social instinct which different kinds of species acquired through evolution can be different from each other. But it will be helpful to look into the origin of proto-morality through comparison to primates, especially chimpanzees. Observation of intuitive moral judgment can be the starting point of evolutionist research. However, it is difficult to conclude that this judgment was presented through evolution. This is because that there can be more than one pattern of intuitive moral judgment. Finally, cross-cultural comparison requires more discussion. In the first place, it is not easy to demonstrate the common moral characteristic of mankind through this comparison, and even if the common character were found, it is difficult to claim that this is due to evolution. But Darwin's explanation of social instinct and phylogenetic explanation of morality to some extent explains why our moral judgments in particular situation differ from each other, but at the same time similar from each other.