This study was conducted to explore the perceptions of Korean adults about what is a happy life and what can make them happy. 61 Korean adults participated in FGI (Focused Group Interview), and content analysis of their responses yielded 18 categories with 148 characteristics of a happy life. The list of 153 items was administered to 517 Korean adults to assess the importance of each item through the 6-point Likert scale. Principal axis factor analysis showed that most factors were unidimensional with moderate reliability. A systematic effort was made to improve the relevance of the list to happy life by removing or adding some items and introducing a new category of religion, which resulted in 156 items with 18 categories. The 156 happy life characteristics were administered to a nationwide sample of 1503 Korean adults in order to assess their happiness through 6-point Likert scale. Responses from 877 participants were submitted to exploratory factor analysis and 58 items with low factor coefficient were deleted. The Happy Life Inventory consisted of 97 items and 16 factors. Confirmatory factor analysis of the responses from the 611 adults showed that the 16 factor structure derived from the exploratory factor analysis was appropriate. Correlation between the factors of happy life and psychological well-being supported the construct validity of the Happy Life Inventory. Finally the implications and limitations of the present study as well as the future directions of this area were discussed.