Urban green spaces have a positive impact on citizens’ mental health and have contributed to improving their quality of life during the COVID-19 pandemic. In South Korea, where more than 50% of all households live in apartments, apartment-complex landscaping space plays the role of urban green space. This study aimed to investigate the relationships among a perceived restorative environment, restorative experience, life satisfaction, and psychological well-being by conducting a survey between residents living in apartments with landscape space. More specifically, an online survey was conducted from 8 to 15 June 2021 among residents in apartment complexes (500 households or more) located in the capital region in South Korea. We applied partial least squares structural equation modelling (PLS-SEM) using 220 samples to test the causal relationship presented in the conceptual model of this study. The results revealed that residents’ perceptions of the restorative environment of landscape space, including fascination, being away, and coherence had positive effects on restorative attention. Among the restorative environmental factors, the higher the “being away”, the greater the effect on restorative attention. Second, the effects of fascination and coherence on life satisfaction were mediated by restorative attention. Third, restorative attention and life satisfaction significantly influenced psychological well-being. Additionally, life satisfaction acts as a mediator in the relationship between restorative attention and psychological well-being. In summary, this study has theoretical implications, in that it explores the effects of apartment complex landscaping space as urban green spaces on residents’ mental health.