Background <p>Japan has experienced widening income disparity in recent years, raising concerns about income inequality in health. This study aims to investigate trends in income-related concentration and inequality in key health outcomes between 2001 and 2022.</p> Methods <p>This study utilized repeated cross-sectional data from 500,580 individuals (238,746 men and 261,834 women) aged ≥ 6 years, obtained from eight waves of population-based national surveys conducted between 2001 and 2022. The study examined trends in the concentration index and the relative and slope indices of inequality for key health outcomes, including self-rated health, subjective symptoms, limitations in undertaking activities of daily living, and experience of stress/anxiety, as well as the number of physician visits and incidence of selected non-communicable diseases (NCDs). All measures were standardized by age and sex.</p> Results <p>Increasing concentrations of poor health status among low-income individuals and rising income-related health inequality were observed over the study period, although a greater pro-poor concentration was noted for physician visits. Additionally, income-related inequality increased for persons with hypertension, diabetes, and at least one type of NCD.</p> Conclusions <p>The results indicate persistent income-related inequalities in health within a context of universal health coverage.</p>