I explored health-relevant poverty line and rate to understand poverty in terms of population health, using data obtained from nationwide population surveys conducted in Japan. First, I searched for a poverty line that maximized the proportion-weighted relative underperformance in health, for individuals living below the poverty line. Second, I searched for a poverty line that maximized the likelihood of the logistic regression model, to explain poverty in terms of health. The results reveal that the health-relevant poverty line should be drawn at a level higher than the conventional 50% or 60% level. Therefore, conventionally defined poverty rate may underestimate poverty, in terms of population health.