Social psychologists have recently begun to explore the problem of free-will beliefs. Philosophers have been working on the problem of free will over the ages, and studies of social psychologists on free-will beliefs are based on past philosophical theories. Meanwhile, philosophers not only argue over the theoretical issue of free will but also engage with the research program of experimental philosophy. This program shares the methodology of social psychology, and experimental investigation of belief in free will is proceeding at a rapid pace. In consideration of the above arguments, it seems obvious that social psychologists need to collaborate with philosophers on the problem of free-will beliefs. The authors therefore review the findings of each discipline and construct a model of people’s free-will beliefs. In this model, we consider free-will beliefs as composed by alternative possibility and agency, and these components function to promote attribution of moral responsibility, self-control, and social fit.