Abstract: In the context of intensifying declining birthrates and growing demannds for educational equity, free preschool education has become an important policy option for countries to reshape public responsibility for early childhood education.Using the three-dimensional framework of new institutionalism—regulative, normative, and cultural-cognitive—to analyze Japan's free preschool education policy, the findings indicate that the policy is not merely a tool for fiscal expansion; rather, it operates through the synergistic interaction of institutional mechanisms, including legal authorization, central-local division of responsibilities, interdepartmental coordination, and fiscal burden-sharing. Over the course of policy evolution, a stable institutionalized logic has gradually taken shape. The implementation has effectively alleviated the economic burden of family childcare, improved the accessibility of preschool education, and exerted some positive effects on educational quality and family fertility expectations. However, the policy process also reveals multiple structural tensions, such as fiscal pressures and central-local responsibility gaming, demand expansion versus uneven regional resource allocation, quality differentiation among institutions, and the inflation of family educational expectations, which may result in deviations from the original policy objectives.

Key words: free education, preschool education, new institutionalism, Japan