Objectives: There are at least three conceptual models for the effects of the childhood social environment on adult health: the critical period model, the social mobility model, and the cumulative risk model. However, few studies have investigated all three different models within the same setting. This study aims to examine the impact of childhood and adulthood socioeconomic positions and intergenerational social mobility over the life course on the health in adulthood based both on the critical period model and the social mobility model. Methods: This study was conducted on 9583 adults aged between 25 and 64 years old and they were the respondents to the Korea Welfare Panel Study (2006). A multivariate logistic regression analysis was carried out, using the critical period model and the social mobility model out of the life course approaches, to look into the impact of childhood and adulthood socioeconomic positions and intergenerational social mobility on the health status in adulthood. Results: Household income and occupation out of the adulthood socioeconomic position indicators had an independent influence on the adulthood health status. The childhood socioeconomic position indicators, except for the place of childhood residence, affected the adulthood health status even after adjustment for the adulthood socioeconomic position. The effect of intergenerational social mobility was also statistically significant even after adjusting for the adulthood socioeconomic position, but it became insignificant when the childhood socioeconomic position was additionally adjusted for. Conclusions: Adulthood health is indeed affected by both the childhood and adulthood socioeconomic positions as well as intergenerational social mobility. This result shows that a life course approach needs to be adopted when dealing with health issues.