This paper is intended as an investigation of A. C. Pigou's ethics. Thus far, few attempts have been made to investigate his philosophical (ethical) side. The point I want to make is that, contrary to the ordinary interpretation, Pigou's ethical idea does not belong to the traditional hedonistic utilitarian view espoused by Bentham, J. S. Mill, and Sidgwick, but to the ideal (i. e., non-hedonistic) utilitarian view originated by G. E. Moore. First, it is notable that Pigou, following Moore, recognizes that “good” is indefinable; he clearly makes a distinction between “What is good?” and “What is the good?” Pigou's response to the latter is as follows. In the hedonistic utilitarian view, the only intrinsically good thing is “pleasure.” Pigou, in his early article (1907), completely disagrees with this thesis. He asserts that pleasure is not the sole good, and that there are plural elements (i. e., not only pleasure but also love, good will, and so on) which are intrinsic goods; they compose a state of conscious life. A state of conscious life, Pigou says, is a complex of many factors such as those remarked above. In describing how a state of conscious life as a complex whole does have intrinsic value, Pigou relates that the goodness of conscious states is, to use a mathematical phrase, a function of several variables, some of which can be specified (i. e., pleasure, love, good will); the dependent variable represents the intrinsic value of the complex whole. In a later article (1932), Pigou discusses a problem quite different from that laid out above: what sort of actions ought to be performed? This is, to put it briefly, a problem of the relation between good and right. In short, Pigou defines right as “the cause of a good result”, which is thus identical with “useful”; he positively affirms that the end (i. e., the intrinsic good) always will justify the means, and any action that is not justified by its consequences can not be right. This is a typical teleological view. It follows from what has been said above that Pigou and Moore make use of the same ethical reasoning when answering two questions: “What is the good?” and “What kind of action ought to be performed?” That is to say, Pigou, as well as Moore, adopts teleology (consequentialism), plurality in the theory of value, and commensurability of plural goods. Further, the commensurability is based on the intuitive idea of good, and then this is a kind of idealism. On these grounds, I have come to the conclusion that Pigou is the ideal utilitarian.