Objectives : The coverage of Korean National Health Insurance is limited to basic level. Korean government encourages private health insurance for covering medical securities. So, many studies examined the determinants of purchasing private health insurance. However, 11% of Korean population is older than 65 in 2011. Considering the elderly is important to establish a health policy. The aim of this study is to examine factors determining the purchase of private health insurance among middle-aged and elderly Korean adults. Methods : We used the second Korean Longitudinal Study of Ageing (KLoSA), selected 8,688 sample of the aged 47 or older for the analysis. KLoSA collected information on demographic characteristics, income, health- related factors. KLoSA data include in the number of outpatient, inpatient, oriental hospital visit, dental clinic visit for two years. Logistic regression was used to examine the relationship between the determinants of purchasing private health insurance and the factors which include age, gender, education, residential district, marital status, smoking, drinking, physical exercise, economic activity status, national health insurance type, income, the number of chronic disease, and the number of outpatient, inpatient, oriental hospital visit, dental clinic visit for two years. Results : People who were older, did not live in a city, had higher IADL, currently drunk alcohol, did exercise regularly and had chronic diseases more than three were inclined not to purchase private health insurance. Females, the married, well-educated, past & currently smokers, the employed, high income earners, national health insurers, metropolitan citizens and someone who got high MMSE were more likely to purchase private health insurance. The more people experienced outpatients, inpatients, dental clinics and Chinese medicine clinics, the more private health insurance was purchased. The elderly people over 75 had more private health insurance than the aged 65-74. The strongest factors for private health insurance is gender, and economic status such as income. Conclusion : In this study, we found healthy-high income people were more likely to purchase private health insurance. In contrast, unhealthy-low income and older people did not. The economic factors were strongly related with private health insurance in aged over 75. These mean inequality exists in the using private health insurance. Therefore, the government should consider vulnerable social group before expanding private health insurance.