The effect of investment is often dependent on the degree of the potential complementarity among industries. However, we frequently find out that enterprises concerned with investment cannot find such a situation, and there are few chances for the occurrence of potential complementarity. However, if banks behave as coordinators among enterprises or as complements to industries, such complementarity can occur and social welfare can be improved. The present study examines the behavior of banks as coordinators and the occurrence of complementarity in the economy.