This research aims to explore the relationship between tenants in co-living apartments and happiness. The research used semi-structured in-depth interview method. The interviewees were 20 to 30 years old and all of their hometowns were outside of Taipei and New Taipei city. 5 interviewees lived or used to live in a co-living apartment in Taipei City due to schooling or work. The main findings are as follows: First, the tenants' traits are similar, the default position before check-in will not affect the adaptation mentality after check-in; furthermore all of them agree that the interaction with others during residence can create happiness and all agree to continue the relationship after moved away. Second, living in a co-living apartment is time-sensitive. Although this place may have the opportunity to be regarded as a "second home" and the internal tenants may have the opportunity to be regarded as a "family-like", but no one will still choose to stay for a long time because of their own career planning. Therefore, it can only be used as a short-stay station rather than a permanent home. At last this study makes two suggestions based on the results of the research, for the researcher who is interested in this related topics in the future.