While quarantine has become a widely used control measure during the outbreak of the 2019 novel coronavirus disease (COVID-19), empirical research on whether and to what extent quarantine and attitudes towards COVID-19 influence psychological outcomes is scant. Using a cross-sectional online survey, this paper is the first to investigate the heterogeneous impact of quarantine experiences and attitudes towards COVID-19 on the whole distribution of psychological well-being in China. We find that credibility of real-time updates and confidence in the epidemic control are associated with a decline in depression but an increase in happiness. Such effects are stronger in the upper distribution of depression and the median of happiness. We also discern that individuals with severe depressive symptoms (or lower levels of happiness) are more susceptible to the severity of the pandemic. Moreover, home self-quarantine is associated a decrease in depression but an increase in happiness, by contrast, community-level quarantine discourages happiness, especially in the lower distribution of happiness.