Cycling is known to be healthy all over the world. In Netherlands, “The Cyclist’s Paradise,” a Dutch research institution demonstrated that the fitness level of employees who are cyclists corresponds to the fitness level of non-cycling colleagues who are five years younger, and, for regular cyclists, to the fitness level of non-cycling colleagues who are even ten years younger. In Japan, lots of local governments are trying to improve town traffic policies and to encourage cycling as a means of transport. Ageo City, where Seigakuin University is located, also published a new cycling town plan recently which led to a reduction of the medical expenses of citizens, the local government, and companies and organizations, according to the project for each organization. In this paper, I try to estimate the amount of social benefits of cycling by means of calculating the reduction of individual medical expenses due to such local cycling projects. I will also attempt to calculate the amount of social cost if individual cyclists have to bear the expense of making cycling lanes to avoid traffic accidents between cyclists and cars or pedestrians.