This study examined whether the relationship between self‐determination loneliness motivation and psychological well‐being in adulthood is mediated by ruminating‐reflective thinking and meaning of life. For this purpose, on the subjects of 438 adults aged 20 to 60 years in Seoul and Gyeonggi‐do, a survey was conducted for self‐determination loneliness motivation, ruminating‐reflective thinking, satisfaction of life, and psychological well‐being. In the results of the structural equation model analysis, first, in the relationship between self‐determination loneliness motivation and psychological well‐being, there was a mediating effect in ruminating thinking and meaning of life, respectively. Second, the dual mediating effect of self‐determination loneliness motivation on psychological well‐being after going sequentially through ruminating thinking and meaning of life was found to be significant. Third, the dual mediating effect of self‐determination loneliness motivation on psychological well‐being sequentially through reflective thinking and meaning of life was also found to be significant. Based on these research results, this study discussed the issues that require considerations to improve psychological well‐being in adults with self‐determination loneliness motivation, and the importance of differentiated counseling interventions considering the characteristics of ruminating thinking and reflective thinking, which affect the meaning of life and psychological well‐being.