Abstract
In this paper, a representation of group decision making situations based on social network theory is provided, and the situations are analyzed by using the Newcomb's balance theory. A group decision making situation consists of multiple decision makers, and they are, as a whole, required to choose one or more alternatives out of a set of all alternatives. Such a situation accompanied with a hierarchical structure of the group of decision makers, social relationships among decision makers, and preferences of decision makers toward alternatives is represented as a signed graph. Then, the analysis of the situation with the Newcomb's balance concept reveals a relationship between stable states of the situation in the Newcomb's sense and the structure of the situation as a social network.
