There are many views about the structure of concepts, a plausible one of which is the theory-theory. Though this view is plausible for concrete concepts, it is unclear that it would work for abstract concepts, and then for moral concepts. The goal of this paper is to provide a plausible theory-theory account for moral concepts and show that it is supported by results in the moral psychology literature. Such studies in moral psychology do not explicitly contend for the theory-theory of moral concepts, but I demonstrate that they actually do provide evidence for the use of theory knowledge at times in moral categorization and decision-making. In philosophy of cognitive science, I newly show that there is evidence that the theory-theory does apply to some moral concepts.