This study examines long-run macroeconomic impacts of population aging in Korea, using the standard Auerbach-Kotlikoff model. The calibration results are broadly consistent with common expectations. First, despite the rapid aging trend, Korea will continue to benefit from its young population for the next few decades. For the growth rate of per capita GDP, however, the negative impact of aging will be manifested sooner. Second, population aging has varying welfare implications for different generations. While generations that enter the labor market before 2030 are expected to suffer, the following generations are expected to benefit from the demographic change. Third, the current national pension system of Korea only increases the welfare of current older generations at the cost of current and future younger generations.