This paper examines the evolution of the systems of innovation approach and its main issues. At first, national systems of innovation have appeared on the purpose to substitute the neoclassical macroeconomic policies. But various criticisms have been raised because of the restriction within national boundary of analysis, the lack of dynamic analysis, the danger of institutional determination, the deficiency of theoretical accuracy in national systems of innovation. Technological systems, regional systems of innovation, sectoral systems of innovation have been developed to overcome criticisms about national systems of innovation. Nevertheless the unsettled questions in the systems of innovation approach remain. The academic and policy-making usefulness of the systems of innovation approach will be expanded by development of the complementary researches within approach.