In this chapter, we analyze the impact of redistributive taxes on equality in household expenditure on private supplementary education using monthly microdata since 2000 from the Statistics Bureau of Japan’s Family Income and Expenditure Survey. Specifically, using Gini coefficient, concentration coefficient, Kakwani index, and Reynolds–Smolensky index values, we compare the temporal changes in redistributive effects and equality in private supplementary education expenditure, and investigate the underlying factors. The findings are as follows. First, the impact of the redistributive effects of taxes on the Kakwani index values for private supplementary education expenditure, measured in terms of after-tax income, is minimal, with variations in the Kakwani index values largely attributable to changes in the concentration coefficient of private supplementary education expenditure. Second, our analysis by school level indicates that in elementary and high schools, the Kakwani index values for private supplementary education expenditure, measured in terms of after-tax income, are low, and equality in private supplementary education expenditure remains lower than that in after-tax income. These results underscore the importance of supporting low-income households, particularly those with children in elementary and high schools, and suggest the value of targeted support in the form of vouchers for private supplementary education.