Objectives: The purpose of this research was to understand the marriage maintenance experience of DINK (Double Income, No Kids) families in their 30s and 40s, and to explore the marriage maintenance process and factors affecting it. Methods: To this end, in-depth interviews were conducted with 12 men and women among DINK couples in their 30s and 40s, and the data were analyzed by applying a grounded theory qualitative research method. Results: As a result of this research, 117 concepts, 46 subcategories, and 21 categories were derived. According to the passage of time, the marriage maintenance process of a DINK family in their 30s and 40s consists of five stages: “inner value defense stage”, “consideration and adjustment stage”, “future life search stage”, “self-awareness internalization stage”, and “life management stage”. The core category was identified as “possessing the inner values of the couple amidst prejudice”. Conclusions: This research is meaningful in that it provides academic evidence to understand the marriage maintenance process of DINK families in their 30s and 40s and to identify practical ways to help them.