Despite its high level of economic development, Korea is known as one of the countries with a relatively low level of happiness. Nevertheless, data for rigorous research on happiness are scarce. To address this, we conducted the “Korean Happiness Survey” to ① track the level of happiness and inequality among Koreans, ② predict various social phenomena, ③ clarify various determinants that determine levels of happiness and inequality, and ④ increase the level of happiness among Koreans. In 2021, a first wave survey was conducted targeting approximately 17,000 citizens aged 15 or older. The average happiness score for Koreans in 2021 was 6.56 points out of 10. However, we also found low happiness scores in vulnerable groups, confirming that inequality is a major problem. It is necessary to suggest policies that can improve happiness through enhancing quality of life for these groups based on these findings.